Choosing & Keeping Discus: A Practical Guide

Discus are among the most distinctive freshwater aquarium fish, but successful discus keeping starts well before you bring your fish home.

The key isn't chasing a single "perfect" number. It is providing a suitably sized, mature aquarium with stable warm water, effective filtration, good nutrition and a maintenance routine that keeps water quality consistently high.

Whether you're considering your first discus or have recently brought a group home, this guide covers the fundamentals you should understand to give them the right start.

Before You Buy Discus

Before choosing individual fish, make sure your aquarium is genuinely ready for them.

Discus are large cichlids that are normally kept socially, so your aquarium needs to accommodate not only the fish you buy today but their adult size and the behaviour of the group. A small aquarium can quickly become difficult to manage as the fish grow and the biological load increases.

Your aquarium should be fully cycled and biologically established before discus are introduced. Ammonia and nitrite should both be zero, and nitrate should be controlled through appropriate stocking, feeding, filtration and regular water changes.

Temperature and other water conditions should also be stable before the fish arrive.

If you're unsure whether your existing aquarium is suitable, ask us before purchasing. Tank dimensions, volume, filtration, existing livestock and water parameters all matter.

Choosing Healthy Discus

Colour and pattern may be what first catches your eye, but health, behaviour and suitability should come first.

When choosing discus, look for fish that are:

• alert and responsive

• swimming normally and maintaining their position comfortably

• carrying their fins normally rather than persistently clamping them

• showing a good overall body condition

• breathing normally rather than showing obvious respiratory distress

• free from obvious wounds, lesions or unusual swellings

• showing normal interest in their surroundings and, where observable, food

Avoid choosing a fish simply because it is the brightest or most dominant animal in the aquarium.

Discus are social cichlids and individuals can establish a hierarchy. A fish that is continually isolated, bullied or unable to compete for food may require attention even if there are no immediately obvious external signs of disease.

Size matters as well. Think about how a new discus will fit with the size and behaviour of an existing group rather than choosing solely on colour.

If you're unsure which discus will suit your aquarium or existing fish, talk to Brisbane Discus before making your selection.

Explore: All Discus
Also useful: New Discus Arrivals

Aquarium Size and Stocking

There isn't one tank-volume formula that works for every discus aquarium.

Adult discus are substantial fish, they are social, and they produce a meaningful biological load. The aquarium therefore needs enough water volume and swimming space for the group while also providing sufficient filtration and access for maintenance.

Published husbandry recommendations vary considerably. For example, established discus breeders may use stocking practices very different from those appropriate for a customer's display aquarium.

For a home aquarium, the important principles are:

• plan for the adult size of the fish

• keep discus socially rather than treating them as solitary display fish

• provide enough space for less-dominant fish to move away from aggression

• leave sufficient biological capacity for feeding and waste production

• consider the additional load created by tank mates

• don't use heavy stocking as a substitute for thoughtful aquarium planning

Larger aquariums generally provide more stable conditions and more flexibility when managing a group.

Before buying a group, we recommend discussing your aquarium's actual dimensions and volume with us rather than relying on a generic litres-per-fish calculation.

Temperature and Water Conditions

Discus are warm-water tropical fish.

For most captive discus, water in the upper tropical range is appropriate. Published specialist guidance commonly places normal discus husbandry around 28–30°C, although the correct conditions can vary with the origin and previous husbandry of the fish.

That last point is important.

Captive-bred discus may be accustomed to quite different hardness, conductivity and pH from wild discus or fish raised by another breeder. For this reason, don't aggressively alter otherwise suitable, stable water simply because you've found a particular pH or hardness value online.

Instead, find out what conditions your discus have been maintained in and aim for suitable, stable conditions.

Whatever water chemistry is appropriate for your fish, the fundamental water-quality requirements remain:

• ammonia: 0 mg/L

• nitrite: 0 mg/L

• nitrate: kept controlled through appropriate maintenance

• stable temperature

• appropriately treated replacement water

• regular testing, particularly in a new setup or after livestock changes

Sudden changes can be more problematic than a stable value that isn't identical to an arbitrary target.

Explore: Water Treatment

Filtration and Oxygenation

Good filtration is central to successful discus keeping.

Your filtration system needs to process the waste produced by the entire aquarium while maintaining stable biological filtration. It should provide effective mechanical and biological filtration without creating an unnecessarily harsh environment for the fish.

Discus naturally favour relatively calm water, so extremely strong currents throughout the aquarium are unnecessary. The goal is effective circulation and filtration while still giving the fish comfortable areas to swim and rest.

Sponge filtration can be particularly useful for biological filtration and aeration, including in breeding, grow-out and quarantine situations. Depending on the aquarium, it may be used alone or as part of a larger filtration system.

Remember that warmer water holds less dissolved oxygen than cooler water. Good circulation and aeration therefore deserve particular attention in a warm discus aquarium.

When cleaning biological filter media, avoid washing established media under untreated chlorinated tap water. Rinsing it gently in removed aquarium water can help preserve the beneficial bacterial community.

Explore: Sponge Filters

Feeding Discus

Good nutrition supports growth, body condition and normal behaviour, but feeding also has a direct effect on water quality.

A quality diet suitable for discus should form the basis of the feeding routine. Depending on the fish and their established diet, suitable foods may include appropriately sized pellets, granules, frozen foods and other diets formulated for discus.

Smaller, regular meals are generally preferable to dumping a large quantity of food into the aquarium at once.

Watch the fish while they eat. This helps you confirm that:

• each fish is getting access to food

• less-dominant fish aren't continually being pushed away

• the food is an appropriate size

• appetite remains normal

• excessive food isn't being left to decay

Remove significant uneaten food rather than allowing it to break down in the aquarium.

Feeding requirements also change with age. Growing juvenile discus can require a more intensive feeding and maintenance routine than established adults. More feeding means more waste, so filtration and water-change frequency need to match the way the aquarium is being managed.

Explore: Discus Food

Maintenance and Water Changes

Consistency is one of the most important parts of discus keeping.

There is no universal water-change percentage that suits every aquarium. Published discus guidance varies because stocking density, aquarium volume, fish age, feeding rate, filtration and source water all differ.

Rather than following a percentage blindly, establish a routine that keeps your aquarium's measurable water quality consistently suitable.

A good maintenance routine should include:

• testing water regularly

• removing uneaten food and accumulated waste

• carrying out regular partial water changes

• treating replacement tap water appropriately

• checking temperature

• checking filters and water flow

• cleaning filter media appropriately when required

• observing every fish for changes in appetite, breathing, colour, posture and behaviour

An aquarium containing heavily fed growing discus may need substantially more maintenance than a lightly stocked adult display aquarium.

Water testing tells you whether your routine is actually working.

Plants and Aquascaping

Discus can be kept in attractive planted aquariums, but the design needs to work for the fish first.

Choose plants that tolerate the warm conditions used for discus. Arrange hardscape and planting so the fish have visual shelter without sacrificing swimming room or creating areas where waste is difficult to remove.

Bare-bottom aquariums are also used successfully, particularly for breeding, quarantine and some grow-out systems, because waste can be seen and removed easily.

Neither approach automatically makes a successful discus aquarium. Water quality, maintenance and appropriate stocking remain more important than the decorating style.

Choosing Tank Mates

A discus community aquarium can work well, but tank mates need to be chosen around the requirements of the discus.

Ask four questions before adding another species:

1. Can it live comfortably at the discus aquarium's temperature?

2. Is it peaceful enough to live with discus?

3. Will it compete aggressively with the discus at feeding time?

4. Will its adult size, behaviour and biological load suit the aquarium?

Suitable warm-water community species are sometimes kept successfully with discus, including selected tetras and catfish, but compatibility should be considered species by species.

Avoid assuming that every fish described as "peaceful" is automatically a good discus companion. Temperature requirements and feeding behaviour can rule out otherwise peaceful community species.

If you're planning a community tank, ask us about the exact species you're considering before adding them.

Introducing New Discus

New fish should never simply be tipped into an established aquarium.

Before they arrive, confirm that the aquarium or quarantine system is heated, cycled and stable.

Where practical, quarantine new fish separately before combining them with an established collection. Quarantine allows you to observe appetite, behaviour, waste and general condition while reducing the risk of introducing a health problem into the main aquarium.

A proper quarantine system should have its own suitable filtration, heater and dedicated equipment. Nets, siphons and other wet equipment can transfer pathogens between aquariums, so cross-contamination should be avoided.

When moving fish between different systems, also consider differences in temperature and water chemistry.

Follow the acclimation advice provided for the fish you have purchased rather than automatically using one method for every situation. Transport duration and differences between transport water and aquarium water can affect the safest approach.

Once introduced, keep the environment calm and watch the fish closely. It is normal for recently moved discus to need some time to settle, but continuing deterioration should not simply be dismissed as settling-in stress.

Don't Medicate "Just in Case"

Medication has an important place when there is a genuine health problem and the correct treatment has been identified, but it shouldn't replace good husbandry.

Avoid adding medications simply because a fish is new, shy or temporarily off its food without first considering water quality, temperature, aggression, acclimation and other environmental causes.

Some treatments can also affect biological filtration or be inappropriate for particular livestock.

If your discus appear unwell, check the aquarium conditions first and seek advice before reaching for a treatment you're unsure about.

Explore: Medication

Common Discus-Keeping Mistakes

Many problems can be avoided by getting the fundamentals right from the beginning.

Buying before the aquarium is ready

A discus aquarium should be cycled, heated and stable before the fish arrive.

Choosing by colour alone

Health, body condition, behaviour, size and suitability for the group are more important than selecting the most striking pattern.

Chasing pH

Repeatedly adding products to force a particular number can create instability. Understand your source water and the conditions the fish are accustomed to before making changes.

Underestimating adult size

Juvenile discus grow. Plan the aquarium for the adults rather than the size of the fish on purchase day.

Keeping an unsuitable social group

Discus are social cichlids with a hierarchy. Stocking needs to consider group behaviour as well as litres of water.

Overfeeding

Extra food doesn't automatically mean better growth. Food left decomposing in the aquarium increases the load on the filtration system and degrades water quality.

Choosing incompatible tank mates

A peaceful fish isn't necessarily suitable if it cannot tolerate discus temperatures or consistently beats them to food.

Ignoring the less-dominant fish

Don't watch only the largest or most colourful fish. Check that every member of the group is eating and behaving normally.

Adding fish without considering quarantine

Every new introduction has the potential to bring pathogens into an established aquarium.

Treating symptoms without checking water quality

When something changes, check temperature, ammonia, nitrite, nitrate and other relevant water parameters early. Poor environmental conditions can cause stress and can make other health problems worse.

When to Ask for Help

Get advice early when something doesn't look right.

Contact Aquarium Haven & Brisbane Discus if you're unsure about your aquarium setup, filtration, feeding routine, compatibility, water conditions or the suitability of a new discus for your existing group.

For an existing health concern, useful information includes:

• aquarium dimensions and volume

• number, approximate size and type of discus

• other livestock

• aquarium temperature

• pH

• ammonia

• nitrite

• nitrate

• filtration

• how long the aquarium has been established

• feeding routine

• recent water changes or new additions

• clear photos or video of the affected fish

• a description of when the behaviour or symptoms started

If a fish is seriously unwell, rapidly deteriorating, injured, showing persistent abnormal breathing or other significant symptoms, seek prompt advice. A veterinarian experienced in aquatic animals may be appropriate for health problems requiring diagnosis.

A Good Discus Aquarium Starts With Consistency

Successful discus keeping isn't about continually adjusting the aquarium or chasing a supposedly perfect set of numbers.

Start with an appropriately sized, established aquarium. Choose healthy fish suited to the group. Keep the water warm, clean and stable. Use adequate filtration, feed a quality diet, maintain the aquarium consistently and pay attention to the behaviour of every fish.

Get those fundamentals right and discus become far easier to understand and enjoy.

If you're planning your first discus aquarium or aren't sure what will suit an existing setup, Aquarium Haven & Brisbane Discus can help you work through the tank size, filtration, water conditions, feeding and compatibility before you choose your fish.

Explore All Discus | New Discus Arrivals | Discus Food