Three published pH bands, and one number in all three
Discus fish care is sold as the hardest job in freshwater fishkeeping, and the argument is almost always about water. This record found something narrower and more useful than that reputation: our three sources publish three different pH bands, and they overlap on a single value. Not a range. One number, 6.8.
Aquarium Co-Op gives 6.8 to 7.6 and flags the field itself, that the recommended pH can be controversial. Aqueon gives 6.0 to 7.0. aqua-fish gives 6.0 to 6.8. The highest floor is 6.8 and the lowest ceiling is 6.8, so that is what this record's pH row prints, and there is nothing else it could honestly print.
The water the fish comes from is more acidic than any of the three. Wikipedia: wild specimens are native to the soft, highly acidic blackwater tributaries of the Amazon basin, where pH values frequently range between 5.0 and 6.0. Every aquarium recommendation we hold sits above the wild range, and one source does not ask for a pH at all: Aquarium Science says tap water for a decorative discus.
That is the shape of this whole record. The fields where our sources agree are tight to the point of being a single figure, and the fields where they disagree are not small disagreements at all. Station 02 has one source calling the temperature everyone insists on unnecessary, and station 03 has water change advice ranging from monthly to daily.
Why this record was written now
- The gap
- Discus fish is one of the two most searched fish left in our keyword map at 14,000 a month, tied with the bristlenose pleco, and Aquarium Co-Op names that fish as one of the few tank mates it will recommend here.
- What it changes
- A floor of 85 °F is the highest on this site, eleven degrees above the goldfish ceiling. It ties the oscar for the largest minimum tank at 75 gallons, for the opposite reason: the oscar is one big fish, the discus is six.
- What it does not
- The growth rate row is blank, and two sources explain why better than a figure would: the final size depends on how the fish was raised rather than on how long you wait.
85 to 86 °F, and one source saying you do not need it
Four sources publish a temperature band. All four contain 85 to 86 °F, which is the narrowest agreement on any temperature row on this site, and one of the four spends a paragraph arguing against the reason the others give.
| Source | Temperature | pH | Hardness |
|---|---|---|---|
| Aquarium Co-Op | 85 to 86 °F | 6.8 to 7.6 | Soft to medium |
| Aqueon | 82 to 86 °F | 6.0 to 7.0 | 1 to 4 dKH, 18 to 70 ppm |
| aqua-fish | 82 to 88 °F | 6.0 to 6.8 | 1 to 8 dGH |
| Aquarium Science, decorative | 76 to 90 °F | Tap water | not stated |
| Aquarium Science, competitive | 82 to 90 °F | 50 to 70 TDS, RO remineralized | not stated |
| Wikipedia, wild water | not stated | 5.0 to 6.0 | Soft, highly acidic blackwater |
Aquarium Co-Op is the most emphatic and gives its reason: we highly recommend 85 to 86 °F, because the discus farms we get them from usually keep their waters at these temperatures. Aqueon gives 82 to 86 and adds a wild figure higher than any aquarium recommendation, that wild Heckel discus prefer water near 90 °F. aqua-fish gives 82 to 88 for a display tank and pushes the floor up for fry, 84.2 to 87.8.
Aquarium Science is the objection, and station 05 explains the distinction it makes. Its band for a decorative discus is 76 to 90 °F, fourteen degrees wide, and its sentence about the consensus is the longest quote on this record for a reason.
The asymmetry is what settles the practical question. A keeper who sets the heater to 86 °F is inside every band we hold, including Aquarium Science's. A keeper who sets it to 78, which Aquarium Science allows, is outside all three of the others. When four sources disagree about a range and one setting satisfies all of them, that setting is what the record carries.
Red, blue and Heckel: one publisher, three different answers
The pH problem in station 01 gets worse when you read one source across its own pages. aqua-fish publishes a general discus guide and separate pages for two named fish, and the three do not agree with each other.
| The page | Scientific name | Temperature | pH | Hardness |
|---|---|---|---|---|
| Raising discus | Not given | 82 to 88 °F | 6.0 to 6.8 | 1 to 8 dGH |
| Red discus | Symphysodon discus | 78.8 to 86 °F | 4.3 to 6.0 | 0 to 4 dGH, 0 to 71 ppm |
| Blue discus | Symphysodon aequifasciata haraldi | 80.6 to 86 °F | 5.5 to 7.5 | 0 to 8 dGH, 0 to 143 ppm |
Read the pH column down. The same publisher asks for 6.0 to 6.8 on one page, 4.3 to 6.0 on the second and 5.5 to 7.5 on the third, and the three do not share a single value between them. The red discus figure is the interesting one, because it is the only aquarium recommendation we found anywhere that sits inside the wild range Wikipedia describes at 5.0 to 6.0. It is also below every other published band on this record.
This is a taxonomy problem wearing a care-sheet disguise. Symphysodon discus is a species Wikipedia recognizes and limits to the lower reaches of the Rio Negro; S. aequifasciata haraldi is a name Wikipedia flags as unsettled, saying whether S. haraldi is indeed distinct from S. aequifasciatus remains to be determined and that if valid it is widespread, but it might just be a color morph. Aqueon adds a third name in one clause, that wild Heckel discus prefer water near 90 °F.
So a discus is a cichlid whose water requirements depend on which discus you have, and neither the shop nor most of the internet will tell you which that is. Our record prints the overlap of the general guides, 6.8, and prints these three rows beside it rather than averaging them into a range nobody published.
A floor of 85 °F is the highest on this site. The ceiling of 86 is ordinary and four records share it, but nothing else here starts anywhere near 85, so the betta is the only other fish record whose band reaches this one at all. Our angelfish stops at 84 and our goldfish at 74. Among the plants, hornwort and java moss both run to 86. The water and health page carries the whole chart, and this record is the bar at the far right of it.
Water changes: monthly, weekly, or every day
This is the field our sources are furthest apart on anywhere on this site. The range is not a few percent. It is a factor of thirty.
| Source | The schedule | What it says about nitrate |
|---|---|---|
| Aquarium Science, decorative | Monthly 50% | The nitrates can float up |
| Aqueon | Weekly 10% to 25% | not stated |
| aqua-fish | 25 to 50%, two to three times a week, or 20 to 30% daily | Ideally below 20 ppm, and below 10 for fry |
| Aquarium Science, competitive | Daily 50% | not stated |
| Aquarium Co-Op | Varies for every aquarium | Under 40 ppm planted, under 20 ppm not planted |
Aquarium Co-Op refuses the question and answers a better one. It says the amount and frequency of water changes really varies for every aquarium, and then gives the target instead of the routine: keep the nitrate level lower than 40 ppm for planted tanks and lower than 20 ppm for non-planted tanks. That converts a chore into a measurement, and it is the only advice here a keeper can check.
aqua-fish is the only source that raises the cost of doing it wrong in the other direction: frequent water changes can cause stress if the parameters fluctuate, and it asks that the replacement water match the temperature, pH and hardness of the aquarium. A daily 30% change of water that is two degrees cooler is not a smaller version of a good water change.
Aquarium Science's position is the one to read twice, because it is about the choice rather than the number: it puts monthly 50% against a decorative tank with gravel and an under-gravel filter, daily 50% against a competitive tank with a bare bottom, and says that one or the other works while halfway measures typically do not work very well. That is the opposite of how a beginner usually reads conflicting advice, which is to average it.
The full record
| Field | Recorded | Where it comes from |
|---|---|---|
| Minimum tank | 75 gal | Two sources give 75 gallons and one gives 55. Aqueon: they require an aquarium of 75 gallons or larger when full grown. Aquarium Co-Op: we personally recommend a 75-gallon aquarium or larger, and it prices the alternative honestly, that you can do a 55-gallon tank, but then you're forced to do a lot of water changes. aqua-fish gives a minimum tank size of 200 liters, around 55 gallons. Aquarium Science states no minimum volume at all for a decorative discus. That puts this record level with the oscar at 75 gallons, the two largest minimums on this site, and for opposite reasons: the oscar is one big fish and the discus is six of them. |
| Temperature | 85 to 86 °F | Four published bands and they all contain 85 to 86 °F, which is the narrowest agreement on any temperature row here. Aquarium Co-Op is the tightest and the most emphatic: we highly recommend 85 to 86 °F, and it gives its reason, that the discus farms we get them from usually keep their waters at these temperatures. Aqueon gives 82 to 86 °F and adds that wild Heckel discus prefer water near 90 °F. aqua-fish gives 28 to 31 C, 82 to 88 °F, for a display tank and 29 to 31 C, 84.2 to 87.8 °F, for fry. Aquarium Science is the widest by a distance and the only source arguing against the consensus, giving 76 °F to 90 °F, 23 to 32 C, for a decorative discus and 82 °F to 90 °F for a competitive one. A floor of 85 is the highest on this site, eleven degrees above the goldfish ceiling of 74. The ceiling of 86 is not unusual and four records share it: the betta, the cherry shrimp, the hornwort and the java moss. |
| pH | 6.8 | Three aquarium sources publish a band, the bands are all different, and they intersect at exactly one number. Aquarium Co-Op: both wild-caught and captive-bred discus do well when the pH levels are between 6.8 and 7.6, and it flags the field itself, that the recommended pH can be controversial. Aqueon: pH should be between 6.0 and 7.0. aqua-fish: 6.0 to 6.8, slightly acidic, and 6.2 to 6.6 for fry. The highest floor is 6.8 and the lowest ceiling is 6.8, so 6.8 is the only value all three support and it is what this row prints. Wikipedia describes water more acidic than any of the three: wild specimens are native to the soft, highly acidic blackwater tributaries of the Amazon basin, where pH values frequently range between 5.0 and 6.0. Aquarium Science asks for no particular pH for a decorative discus and says tap water, and reserves 50 to 70 TDS water, RO water slightly remineralized, for a competitive one. Aquarium Co-Op adds that if you are focused on breeding and raising discus fry you need much lower pH and water hardness. |
| Hardness | 18 to 70 ppm | Two sources publish a figure and they use different units for hardness, which this site has hit on three records now. Aqueon gives hardness between 1 and 4 dKH, converting it itself to 18 to 70 ppm, and dKH is carbonate hardness. aqua-fish gives soft water as preferred at 1 to 8 dGH, general hardness, about 18 to 143 ppm, and 1 to 4 dGH for fry. The two overlap from 18 to 70 ppm in the numbers as published. Aquarium Co-Op does not give a figure and says discus are usually fine with soft to medium hardness. |
| Adult size | 5 to 7 in | Aquarium Co-Op: usually 5 to 7 inches in diameter if you're doing things right, and it is the only source that ties the figure to the keeper. Wikipedia measures length rather than diameter and is smaller: discus typically reach up to 12.3 to 15.2 cm, 4.8 to 6.0 in, but captives have been claimed to reach 23 cm, 9 in. It also gives a weight nobody else does, adults generally weighing 150 to 250 g, 5.3 to 8.8 oz. aqua-fish: typically about 12 to 15 cm, 5 to 6 inches, though some individuals can reach up to 20 cm, 8 inches. Aqueon says only that discus grow to be quite large. The shape is the part that matters for a tank: this is a fish measured across rather than along, and it is the reason every source asks for a tall aquarium. |
| Diet | Omnivore, and small mouthed | Wikipedia gives the wild diet with a figure nobody else has: they primarily feed on algae, other plant material and detritus, periphyton, but also eat small invertebrates, and invertebrates can make up 38% of the stomach content in wild S. aequifasciatus during the high-water season. Aqueon calls them omnivores and names its own flakes, granules, algae rounds and shrimp pellets, with the only feeding schedule any source gives: feed only what they can consume in 2 to 3 minutes, once or twice a day. Aquarium Co-Op works from the mouth, that because they have small mouths they enjoy feeding on bloodworms, Hikari Vibra Bites and all sorts of frozen foods, and it names prepared foods, frozen or live brine shrimp, blackworms and live microworms. It also adds a warning about one food: discus can get addicted to them quite easily, about frozen bloodworms. aqua-fish is the only source with a recipe, 250 g of beef heart with fat and sinew removed, mixed with garlic, vitamins and spinach, to be fed sparingly with excellent filtration to handle the organic load. |
| Water column | Mid water | No source on this record states a layer in the words our other records use, so this is read from what they describe rather than quoted: a tall bodied cichlid that our sources photograph and describe among broadleaf plants and driftwood in open mid water. Wikipedia adds the behavior that decides the tank rather than the layer, that they are highly social, typically occurring in groups that may number many dozens of individuals, which is unique among cichlids of the Americas. |
| Lifespan | 10 to 15 years | One source publishes a lifespan and it is not a care sheet. Wikipedia: in home aquariums, discus live for an average of 10 years, but can live up to 15 years. It also gives the figure that matters for anybody buying juveniles, that sexual maturity is reached in a year. Aquarium Co-Op, Aqueon, aqua-fish and Aquarium Science publish no lifespan at all between them. |
| Growth rate | Not recorded yet | No source publishes a rate, and two say something more useful about growth than a number would be. Aquarium Science: the ultimate size they reach is determined by how they are raised, and the larger the competitive discus, the more likely it is to win awards. aqua-fish warns about what that means in a shop, that juveniles with unusually intense coloration may have been hormone-treated or are stunted. Aquarium Co-Op notes only that discus take longer to reach full adult size compared to other cheaper fish like guppies. Wikipedia's one year to sexual maturity is the closest thing to a timescale anybody gives. |
The same nine fields for every animal on this site are in the A to Z index.
Where our sources disagree
Every record here names a disagreement. On this one the whole hobby is on one side and one source is on the other, about the single figure this fish is famous for.
Aquarium Co-Op
We highly recommend 85 to 86°F, because the discus farms we get them from usually keep their waters at these temperatures.
Aquarium Science
So many well meaning but ill informed individuals on social media (and YouTube video makers!) recommend high temperatures, bare bottom tanks, and 50% water changes with vacuuming every day as "essential" for ALL discus. This is NOT needed if one is only wanting to grow reasonably sized, healthy, colorful discus in a decorative aquarium.
What we record: we print the overlap and name the objection, because the two positions are not quite about the same fish. Aquarium Science splits discus into decorative and competitive, and its 76 to 90 °F band is for a decorative fish in a tank with gravel and an under-gravel filter and monthly 50% water changes.
Its competitive figures are different in every field. Nobody else on this record makes that distinction at all, which is why their bands are narrower. What can be said without choosing: all four published bands contain 85 to 86 °F, so a keeper who sets the heater there is inside every source we hold, including the one that says they did not have to.
The reverse is not true. A keeper who sets it to 78, inside Aquarium Science's range, is outside all three of the others.
Decorative or competitive: the distinction only one source makes
Every disagreement on this record comes back to one thing. Aquarium Science is describing two different projects under one fish, and nobody else on this page separates them at all.
A decorative discus, in its account, gets 76 to 90 °F, tap water, gravel in an under-gravel filter, monthly 50% water changes, and nitrates that can float up. A competitive discus, the fish grown for a show bench, gets 82 to 90 °F, 50 to 70 TDS water which is RO slightly remineralized, a bare bottom tank, and daily 50% water changes.
It also states the thing that makes the second list make sense: the ultimate size they reach is determined by how they are raised, and the larger the competitive discus, the more likely it is to win awards. The daily water changes are not keeping the fish alive. They are making it bigger.
Why that matters for reading every other source
The other four sources on this record are describing a display tank, so their bands are narrower and their advice is more expensive than Aquarium Science thinks a display tank needs. None of them is wrong on its own terms. What none of them says is which project the reader is on.
It also explains the bare bottom question, which our sources answer three ways. aqua-fish: bare-bottom tanks are preferred by breeders, and general tanks can use fine, dark sand. Aqueon: sand or fine to medium grade, smooth-surfaced gravel, with large broadleaf plants and driftwood. Aquarium Science puts gravel and an under-gravel filter in a decorative tank and the bare bottom in a competitive one.
Our own position is the one the site always takes: we print the figures each source publishes and name the source beside each one, and where a source draws a distinction the others do not, we print the distinction rather than flattening it into an average.
Buy twelve to keep six, and buy them together
Every difficulty in this station comes from the fish being a cichlid. Three sources give a group size and not one of them is a single fish. Aquarium Science: they need to be in groups of at least six to do well. aqua-fish: they should never be kept alone or in pairs, except during breeding, and asks for at least five individuals. Wikipedia explains the number, that discus are highly social, typically occurring in groups that may number many dozens of individuals, which is unique among cichlids of the Americas.
Aquarium Co-Op turns that into the most specific buying instruction on this record: buy 10 to 12 juveniles all at the same time for your 75-gallon tank, with the goal of a nice, relatively peaceful group of six adult discus. Two details in that sentence are the whole point. All at the same time, and ten to twelve to end with six. It also asks for them to be approximately the same size so that no one gets outcompeted.
The reason the group has to be large is the same reason it is calm. Aqueon: generally calm, peaceful fish, but as cichlids, they can be aggressive toward one another. Aquarium Co-Op: they may start to bully each other if you don't have a decent-sized group. Wikipedia adds what happens when a pair forms, that when breeding the pair moves away from the group, possibly to reduce the risk of cannibalism of the young.
Our tank mates page runs on one group per layer, and this record is the most expensive version of that rule on the site: six adult discus is one layer of one species in seventy five gallons, and Aquarium Co-Op's advice is to consider starting with a discus only tank.
Tank mates: two sources, and one fish on both lists
Two sources name species and they disagree about one of them by name. Three of the fish they name have records here.
| Source | Names as suitable | Names to avoid |
|---|---|---|
| Aquarium Co-Op | Cardinal tetras, Sterbai cory catfish, maybe a bristlenose pleco | Speedy, bullet-shaped fish like barbs or huge schools of tetras, clown loaches, German blue rams, angelfish |
| Aqueon | Cardinal tetras, neons, emperor and rummynose tetras, clown loaches, dwarf cichlids | not stated |
| aqua-fish | Corydoras, cardinal tetras, rummy-nose tetras, otocinclus, small plecostomus, ram cichlids | Tiger barbs, large cichlids, goldfish, serpae tetras, gouramis |
Read the clown loach across the table. Aquarium Co-Op names it among the fish to avoid; Aqueon names it among the suitable companions. The same split runs through the dwarf cichlids: Aqueon and aqua-fish both name ram cichlids as suitable and Aquarium Co-Op names German blue rams as one to avoid. Both of those fish now have records here, and the ram record settles which way to read the split: our german blue ram record carries Aquarium Co-Op naming discus among that fish’s own tank mates, on its own ram guide. The same publisher is on both sides, from two of its pages, and the water leaves one degree: that record runs 84 to 85 °F against 85 to 86 here.
Three of the fish named do have records. Our corydoras record is on aqua-fish's suitable list and on Aquarium Co-Op's as the Sterbai species, and its temperature band of 72 to 82 °F stops four degrees below this record's floor. Our otocinclus is on aqua-fish's list and stops at 79. Our bristlenose pleco is the one Aquarium Co-Op will allow, and it stops at 79 as well.
So the water arithmetic contradicts the compatibility advice, and it does so for every named tank mate we hold a record for. Every fish on those suitable lists that we can check has a published ceiling below 85 °F. That is not a claim any of our sources makes and it is not a reason to ignore them; it is the reason our stocking calculator answers from temperature bands rather than from lists of names.
Aquarium Co-Op's own conclusion points the same way. Its advice is not to get so many tank mates, or else the discus may lose out, and to consider starting with a discus only tank. aqua-fish names goldfish among the incompatible, which our goldfish record makes obvious from the water alone: 68 to 74 °F against 85 to 86.
A small mouth, and a recipe involving a heart
Wikipedia gives the wild diet with a figure nobody else has: they primarily feed on algae, other plant material and detritus, but also eat small invertebrates, and invertebrates can make up 38% of the stomach content in wild S. aequifasciatus during the high-water season. A fish whose diet shifts with the river is a fish that will take most things in a tank.
Aquarium Co-Op starts from the anatomy, that because they have small mouths they enjoy feeding on bloodworms, Hikari Vibra Bites and all sorts of frozen foods, and it names prepared foods, frozen or live brine shrimp, blackworms and live microworms. It also gives the one warning on the page about a food rather than a parameter: discus can get addicted to them quite easily, about frozen bloodworms.
Aqueon is the only source with a schedule: feed only what they can consume in 2 to 3 minutes, once or twice a day. On this record that instruction does double duty, because the water change argument in station 03 is really an argument about how much food goes into the tank in the first place.
Beef heart, and why it is on this page
aqua-fish is the only source that publishes a recipe: 250 g of beef heart with fat and sinew removed, mixed with garlic, vitamins and spinach. It attaches two conditions to it, to feed sparingly and to ensure excellent filtration to handle the organic load.
We print it because it is what a named source states, and we print the conditions with it because they are the point. A food that requires excellent filtration is a food that produces the nitrate the water change argument is about. Nothing else on this record connects the two fields as directly.
What to watch for in the shop
aqua-fish gives the one consumer warning any of our sources publishes about this fish: juveniles with unusually intense coloration may have been hormone-treated or are stunted. Aquarium Co-Op gives the other, advising a beginner away from the $300 adults that may die from your lack of experience.
The fry eat their parents, in a manner of speaking
Wikipedia describes something on this fish that no other record on this site has: adult discus produce a secretion, discus milk, through their skin, on which the larvae live during their first 4 weeks. Aqueon describes the same thing from the other end, that the young feed on heavy body mucus secreted by the parents.
Wikipedia also gives the schedule of the weaning, which is the part that reads like a mammal: during the first two weeks, the parents stay near their young allowing them to feed easily, and in the last 2 weeks they swim away, resulting in the young being gradually weaned off. Brood care is highly developed with both the parents caring for the young.
Aqueon is realistic about the first attempt: they pair up and spawn relatively easily, but young, inexperienced parents may eat their eggs. Aquarium Co-Op is blunt about the work, that tank conditions must be pristine for breeding and raising fry, that it is very time and labor-intensive, and that for breeding and raising fry you need much lower pH and water hardness than for keeping them. aqua-fish gives the fry figures: 84.2 to 87.8 °F, pH 6.2 to 6.6, 1 to 4 dGH, nitrate below 10 ppm and daily water changes of 10 to 20%.
Our breeding page exists because most of our records cannot answer the fry question at all. This one can, and the answer is unlike everything else on that page: the first food is the parents.
Discus fish facts: they recognize each other by the face
This is the first record on this site to cite a peer-reviewed primary paper rather than a care source. Satoh, Tanaka and Kohda, in PLoS One in 2016, tested whether discus recognize each other by their faces, using digital models that combined one fish's face with another fish's body.
The result, in the authors' words: focal fish frequently performed partner-specific displays towards partner-face models, and did aggressive displays towards models of non-partner's faces. A model with a partner's face and a stranger's body got the partner display; a model with a stranger's face and the partner's body got the aggressive one. The paper calls this the second documented instance of individual facial recognition in fish, and says the fish use lateral facial color patterns rather than frontal views.
The experiments used eight fish in four pairs and then twelve fish in six pairs, on Symphysodon aequifasciatus, which is one of the species Wikipedia lists.
Why this is on a care record and not in a trivia box: the paper is about a monogamous fish that can tell one individual from another, and every care source on this page asks you to buy ten to twelve juveniles at once and let six of them sort out a hierarchy. Aquarium Co-Op's advice not to let kids tap on the glass, to limit the traffic near the tank and not to put the aquarium next to a TV with loud noises and flashing lights reads differently once you know what the fish is capable of noticing.
What this record will not answer
A water change schedule
Our sources range from 50% monthly to 20 to 30% daily, and one of them says the halfway version works worst of all. The record prints all five positions in station 03 and picks none. What it can give you instead is the number Aquarium Co-Op puts in place of a schedule: nitrate under 40 ppm in a planted tank and under 20 in one without plants.
A growth rate
Blank, and for a better reason than usual. Aquarium Science states that the ultimate size they reach is determined by how they are raised, and aqua-fish warns that a juvenile with unusually intense coloration may have been hormone-treated or stunted. A growth rate would imply that time is the variable, and both of those sources say it is not.
How many species there are
The scientific name row says Symphysodon spp. and stops. Wikipedia records three species from a 2006 review, five main groups from a 2011 molecular study, and that whether S. haraldi is distinct from S. aequifasciatus remains to be determined, since it might just be a color morph. Aqueon says at least three have been described. This is the third record here whose species question our sources cannot close, after java moss and the bristlenose pleco.
Whether a discus tank can be a community tank
Our sources name tank mates and our records contradict the water. Every named companion we hold a record for has a published temperature ceiling below this record's floor. We are not going to resolve that by choosing which source to believe, and station 07 prints both halves.
Discus fish questions, answered from the record
What are discus water parameters?
85 to 86 °F, pH 6.8, and 18 to 70 ppm hardness, which is what is left when you overlap every band our sources publish. The pH figure is a single number rather than a range because the three published bands, 6.8 to 7.6, 6.0 to 7.0 and 6.0 to 6.8, meet at exactly one value. Wild water is more acidic than any of them at pH 5.0 to 6.0.
What tank size do discus fish need?
Seventy five gallons, from two sources. Aqueon: an aquarium of 75 gallons or larger when full grown. Aquarium Co-Op recommends 75 or larger and says you can do a 55-gallon tank, but then you're forced to do a lot of water changes. aqua-fish gives 200 liters, around 55 gallons. That ties this record with our oscar for the largest minimum on this site, and the reason is different: the oscar is one fish and the discus is a group of six.
How many discus should I keep together?
Six adults, and you buy more than six to get there. Aquarium Co-Op: buy 10 to 12 juveniles all at the same time for your 75-gallon tank, aiming for a group of six adult discus, all approximately the same size. Aquarium Science says at least six. aqua-fish says never alone or in pairs and asks for at least five. Wikipedia records wild groups of many dozens.
Do discus really need 86 °F?
Our sources split, and the split is the most interesting thing on this record. Aquarium Co-Op highly recommends 85 to 86 °F because the farms it buys from keep them there. Aquarium Science says the high temperatures social media calls essential for all discus are not needed if you only want reasonably sized, healthy, colorful discus in a decorative aquarium, and gives 76 to 90 °F. Setting 86 satisfies every source we hold; setting 78 satisfies one.
How often do you change water for discus?
Anywhere from monthly to daily depending on which source you read, which is the widest disagreement on this site. Aquarium Science: monthly 50% for a decorative discus, daily 50% for a competitive one, and it says one or the other works while halfway measures typically do not. Aqueon: weekly 10 to 25%. aqua-fish: 25 to 50% two to three times a week, or 20 to 30% daily. Aquarium Co-Op declines to give a figure and gives a target instead, nitrate under 40 ppm planted and under 20 unplanted.
Are discus fish good for beginners?
Three sources answer and none of them says yes outright. Aqueon: not for beginners for a variety of reasons. Aquarium Science: not a beginner fish, but not as difficult as many experts say. aqua-fish: not your average beginner fish, though a beginner willing to learn and invest time can succeed. Aquarium Co-Op writes for beginners directly and advises against the $300 adults that may die from your lack of experience.
Are discus fish aggressive?
Calm with other species and difficult with each other. Aqueon: generally calm, peaceful fish, but as cichlids, they can be aggressive toward one another. Aquarium Co-Op says they may start to bully each other without a decent-sized group and asks for fish of similar size so nobody is outcompeted. Wikipedia adds that a breeding pair moves away from the group, possibly to reduce the risk of cannibalism of the young.
What do discus fish eat?
Most things, through a small mouth. Aquarium Co-Op names bloodworms, Vibra Bites and frozen foods, plus brine shrimp, blackworms and microworms, and warns that discus get addicted to frozen bloodworms easily. Aqueon calls them omnivores and gives the only schedule anybody publishes: what they can eat in 2 to 3 minutes, once or twice a day. aqua-fish publishes a beef heart recipe with 250 g of beef heart, garlic, vitamins and spinach, to be fed sparingly with excellent filtration. In the wild, Wikipedia says invertebrates can be 38% of the stomach content during the high-water season.
Can discus live with angelfish?
Aquarium Co-Op names angelfish among the fish to avoid in a discus tank. The water says the same thing without needing an opinion: our angelfish record carries 78 to 84 °F and this record carries 85 to 86, so the two bands do not touch. They are both tall bodied Amazonian cichlids that ask for a similar tank, which is exactly why the question keeps being asked.
Can discus live in a planted tank?
Two sources say yes and name plants. Aquarium Co-Op: anubias, java fern, bacopa, sword plants and micro swords. Aqueon: large broadleaf plants and driftwood. Our java fern record is the only one of those plants written here, and its temperature row is 72 to 82 °F, which stops three degrees below this record's floor. Aquarium Co-Op also gives a different nitrate ceiling for a planted tank, 40 ppm against 20.
How long do discus fish live?
Ten to fifteen years, from one source. Wikipedia: in home aquariums, discus live for an average of 10 years, but can live up to 15 years, and sexual maturity is reached in a year. None of our four care sources publishes a lifespan at all, which is worth knowing when a shop quotes one.
How big do discus fish get?
Five to seven inches across. Aquarium Co-Op: usually 5 to 7 inches in diameter if you're doing things right. Wikipedia measures length instead, 4.8 to 6.0 inches, with captives claimed to reach 9, and gives a weight of 150 to 250 g. aqua-fish: 5 to 6 inches, some to 8. The measurement that matters is the one across the body, because it is what sets the tank height.
What is the best substrate for discus?
A discus fish tank setup has three decisions in it that our sources answer differently, and the substrate is the one that depends most on which of the two projects station 05 describes. Aquarium Science puts the bare bottom with a competitive discus and gravel in an under-gravel filter with a decorative one. aqua-fish says bare-bottom tanks are preferred by breeders and that general tanks can use fine, dark sand. Aqueon asks for sand or fine to medium grade, smooth-surfaced gravel. Nobody says a display discus must have a bare floor.
What is discus milk?
A skin secretion the fry eat. Wikipedia: adult discus produce a secretion, discus milk, through their skin, on which the larvae live during their first 4 weeks, and Aqueon calls it heavy body mucus secreted by the parents. Wikipedia also gives the weaning, that the parents stay close for the first two weeks and swim away for the last two.
Is it spelled discus or discuss?
The fish is a discus, named for the shape rather than for anything anybody said about it. Wikipedia files the genus as Symphysodon, colloquially known as discus or discus fish, and the common name follows the flat disc of the body, which is also the figure our size row records.
What a discus tank needs that a community tank does not
Three things our sources ask for, and one of them is a water change schedule rather than an object.
- A heater that will hold 86 °Fand a room that will not fight it
- A water change routine, chosen and keptour sources range from monthly to daily
- Air stonesnamed by one source, and warm water holds less oxygen
Every item our records ask for is gathered on the tank setup topic.
Nothing here is a paid link. It is the shortfall between what this record asks for and what a boxed kit contains.
How this record was compiled
- By
- Verified
- Sources
Aquarium Co-Op, discus care guide, Aquarium Science, 17.11 discus, Aqueon, discus care guide, aqua-fish, guide to raising discus, Wikipedia, Discus (fish) and Satoh, Tanaka and Kohda, PLoS One, 2016
- Conflicts
Printed above: three pH bands that meet on one number, four temperature bands and one source saying the high figure is not needed, and water change advice ranging from monthly to daily
- Blanks
Growth rate stay empty until a source we trust states them
- Not recorded
A growth rate, because no source publishes one and two of them say the final size depends on how the fish was raised rather than on time; and a single water change schedule, because our sources range from 50% monthly to 20 to 30% daily and one of them says the halfway version works worst of all