Are discus really that difficult to keep?

Chris Ingham Discus Fish 1 Comment

For years many hobbyist have said that discus are difficult fish to keep, years ago many said impossible to keep. Easy for me to say I know after over forty years of fish keeping. But now we are all armed with up to date knowledge we now know about them, discus are not as difficult to keep as you might have imagined. Even today, many new discus hobbyists keep discus in the same conditions as normal tropical fish. The discus look great and are swimming around, feeding and getting on great with cardinals, neon’s, Cory cats and all the other compatible fish that can be kept with discus. All is well for a short time, and then they get problems. The discus turn dark or even go black, go off eating and sulk off into a corner and gradually fade away. The fish are then deemed as being hard to keep and get the blame for going wrong. So what has happened? What has gone wrong? The answer is easy, and it is as easy as 1,2,3.

It all starts with number one, correct conditions. Water is the first thing to get right first as we have already looked at. If you don’t have the correct conditions, you will never successfully keep discus. If you keep your water parameters right, discus are then just as easy to keep as any other tropical fish. The old saying that has been said many times is very apt here, and that is. Look after and get the water right, and the fish will look after themselves. So how do we create the right conditions? First of all you will need a mature biological filtration system, because one thing discus will not tolerate for long is Ammonia. If you have a fully matured filter, you should not have any Ammonia present which will improve your success rate ten fold. If your tank has been set up and running for a long time, you could safely add your discus once you have carried out a good 25% water change and checked that all the readings of the water test are where they should be and correct. As soon as any water, be it pure RO water, HMA water, or even the best fresh spring water. Once it is placed in your stocked discus tank, it will start to loose its quality because of the fish waste and food that is dissolved in the water. This is why we need some sort of filter to maintain the aquarium water to a high standard to remove the waste, staining and toxins from the water. Take it from me, if you don’t, your discus will soon let you know.

The principle of biological filtration is to build up in sufficient numbers a colony of friendly bacteria to break down the waste (ammonia) from the fish into less harmful nitrite and then nitrate, this is known as the nitrification and denitrification process. This process is known as the nitrogen cycle. To explain the waste products or fish excretion from the fish will give off ammonia in the water and obviously if not diluted down will increase and would not be pleasant for the fish who have to live in it. This is where a good biological filter will do wonders for any fish tank, not just discus. First of all the filter must be mature and house good friendly bacteria (such as nitrosomonas sp) in enough numbers to deal with the job ahead, and that is to break down the ammonia into less harmful nitrites (NO2). But this is still harmful to the fish; so then the biological filter will break this down further into nitrate (NO3) which will not harm the discus. This is why a good adequate filter is needed for any aquarium not just discus but for any fish, although some fish are more resistant to it than discus which will only tolerate ammonia for short periods. Goldfish for example will tolerate ammonia as high as 500 ppm with discus only tolerating 20 ppm. Good water changes on a regular basis will help to reduce the nitrate levels which if allowed to reaching high levels will contribute to algae growing over your plants, rocks and the sides of the tank. Strong sunlight or lights left on for extended periods will also have an effect on ugly algae.


With so many types of filters available, how do you know which one to get, or will be the one you need? The first thing to ask is, are you having a discus only tank, a discus community tank, or are you hoping to breed them? This makes a difference to the type of filters you will need. To explain, if you are planning on breeding your discus, sponge filters will be the best way to filter the tank water. Nowadays, we are very lucky to have very efficient sponge filters made to the highest spec. For example, two large sponge filters would be perfect for a breeding tank. One can be cleaned and serviced at a time, so not to disturb the beneficial bacteria colonies that will be harboured in them. Plus extra air will be pumped through, smashing up the water surface and ensuring perfect oxygen levels within the tank. Any good sponge filter is needed for breeding tanks, because the baby discus fry will be so small, that they would be taken into other filters and killed. Because sponge filters have very fine spores on them, the fry just can’t be sucked into the sponge. This why all the top discus breeders use sponge filters on their discus breeding farms. So what if you don’t want a sponge filter to look at in your tank? Some can be quite large and look unsightly in a well-decorated aquarium. What other options are available? Well under gravel filters have stood the test of time, and worked well for decades. To this day I still use this type of filter on a display discus tank in my fish house, because apart from doing a good job, it looks natural and pleasing to the eye. One problem is if the discus breed, many free-swimming fry hide within the gravel bottom and get stuck between the small stones, and die. So this type of filter is not ideal for maximum numbers of production of young discus if they breed. This type of filter works very simply by having a plastic tray with a void space under the gravel bed. This has hundreds of small slots or holes to let water filter down through a gravel bed. The water is then drawn through the slots leaving behind the gravel, and is drawn up through the plastic airlift tubes and clean filtered water is returned to the tank. This type of filter works mostly on an airlift system. But power heads can be fitted to the tops of the uplift pipes, and this time the water is pumped by these power heads by means of a small under water pump.

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External power filters
Many other options can include external power filters, which put simply are an out side plastic bucket with a water pump on the top. The water pump draws water out of the tank and into the filter which are normally made out of plastic. The water is then passed through filter media which will filter the water, before returning back to the tank clean, clear and Ammonia free. These filters are ideal for discus display tanks, because they have very little equipment in the tank, and will filter heavy loads of tank water. For the return on this type of filter, a spray bar makes an ideal way of splashing small jets of water back into the tank to increase the oxygen in the tank. Also the main component of the filter (the bucket) can be hidden under the tank, and out the way. I have tried air driven external filters in the past, but found these not ideal because they are hard to maintain and difficult to work with. They can also be a pain to get working, and look unsightly hanging off the side of the tank. They also cannot turn over the water enough to keep quality discus water. You will need to turn over at least four times the total amount of water. This is a good tip to remember when buying any type of filter, and easy to remember. For example if you have a seventy-gallon discus tank, you will need a filter that will pump at least 280 gallons per hour. If your filter will not do this, you will need to buy a second filter to back it up. In fact two 140 gallon filters would be better in the long run, because you could maintain one at a time in case you destroy too many of the filter friendly bacteria.

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Internal filters can make good filters for discus tanks as long as a few things are remembered. Some can be very powerful and be very fast. This can upset discus which have high-sided bodies, and could be blown around the tank making them feel very unsettled. Many have controls on them to slow the flow rate down. If this is done, and the water jets spraying across the top of the tank, this is ideal and will not upset your discus. Also using this way extra air is normally sucked into the return outlet, which again will increase oxygen levels in the tank which discus will appreciate. Internal power filters use normally sponges as a filter media, so it would be a good idea as with most filters to use two smaller filters, than one large one. What ever filter method you decide on using, never, ever wash out the filter media with tap water. This will wash out and kill all the beneficial bacteria in the filter, which in turn will make your tank, go through new tank syndrome, which will upset your discus. Nothing will be able to control or keep down the toxic Ammonia, and discus will not tolerate high levels of Ammonia for very long.#

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Not every one will be able to use these, as they can take up a lot of room. This type of filter is normally made of glass, and commonly used smaller fish tank are used for this duty. Sump filters can filter large amounts of water, making them ideal for very large aquariums or fish houses or breeders with many tanks linked up together. They will also add water volume to the main tank, or tanks, which will make the water quality more stable. Any changes in larger amounts of water will cause less stress on the fish. In smaller tanks, any changes in pH for example will be much quicker to rise or fall and cause more stress than in larger aquariums. Trickle towers can be added to sump filters, which will increase the oxygen level ten fold. Trickle towers are the best way as far as I am concerned to filter any tank if possible, because they are the most effective way to break down ammonia. As water falls down through the filter media in the tower, it is mixed with air increasing the oxygen dissolved in the water. It is possible to hide a sump filter under a tank that is sat on a cupboard type stand. This way it is easy to maintain and get to, also all the heaters etc can be hidden in the sump out the way of the main tank.  Sump filter can normally be made by the standard DIY hobbyist. The filter is held back by glass panels that have been siliconed in place. The water then travels through the sump in an ‘up and over’ manner, with a water pump place at the end to pump water back to the main tank.


A CHANGE WILL DO YOU GOOD.  At the end of the day, without filters and good water management, your treasured fish would be living in their own toilet. This is why it is so important to understand why we need the best filtration for our discus, backed up with good regular water changes. I have said this before, and it can’t be said enough time because people forget. But skimp on water quality, and your fish will let you know. Even with good filters, you will still need to change your discus water 25% minimum every week. If this can be done twice a week, even better.


  1. To prolong the life of your filters, make sure you regularly maintain them.
  2. Make sure you remove, and clean any impeller shafts every month, and replace them every 12 months of operation.
  3. Any poly wool pads will need cleaning, or replacing every week for best effect.
  4. Check every day that your filters are working correctly.
  5. If you are unlucky to get a power cut, remember that the beneficial bacteria will die after four hours if any filters are turned off.

Full size picture to wrap around the book cover.

Perfect water in the natural discus world. Perfect water perimeters for keeping discus:

  • Ammonia zero
  • Nitrite zero
  • Nitrate as low as possible but not so important as the first two.
  • PH 6.5 (7 for younger discus is fine)
  • Temperature around 86°f / 30°c
  • GH 3-5
  • KH 3-5
  • ORP 300 or higher the better as your oxygen levels will be better.

Remember, high water temperatures = low oxygen rates. So plenty of aeration in the discus aquarium is desired by the inhabitants. The next secrete for success is, correct regular maintenance. You will need to do at least a minimum of 25% water changes every week, twice a week even better. So if this is not something you can’t do, think hard about keeping discus first. If you don’t do at least 25% changes every week, your discus will soon let you know.

A discus tank next to a busy doorway is not a good idea.

Discus next to a doorway, really?

Something worth considering is forward planning of where you site and set up your discus tank. If the tank is sited where running children suddenly run past the tank out of nowhere, your discus may become unsettled, and frightened. I had a tank placed by a white glossed door some years ago. Where the bright white door was opened, the discus went mad, and shot around the tank as if launched from a catapult. Sunny days were even worse, with reflection of bright light shinning on the gloss paintwork reflecting into the tank, drove my discus insane. Wooden flooring and floorboards are also something worth thinking about. The vibration from just walking past a tank sited on wooden flooring can frighten any fish, not just discus. A friend of mine once used a wooden shed to set up a fish house and to breed angelfish. Every time anybody went into the shed, all the fish went berserk, and you found yourself creeping quietly in to have a look at the fish. After he moved his fish house and set the shed up on a solid concrete base, his angelfish bred and everything went great. Discus would have been exactly the same if placed in this situation. So we are beginning to see, not only discus, but also any kinds of fish really do need the correct conditions and criteria for success. Real plants in a discus tank look great, but please bare in mind that discus in the wild eat plant life. It has happened in the past that a discus keeper has spent a lot of money planting out a discus tank, and discus have cleared the tank and enjoyed an expensive meal. Others have used real plants and the discus have not touched them. But it is worth knowing that your precious plants could possibly disappear. Also if you do use real plants to aquascape your tank, suitable lighting will need to be used or the plants will die. This can be bright for discus and may make them hide away. So some floating plants would be appreciated for cover if you do venture down this road.


CORRECT DISCUS DIET. Discus, unlike any other tropical fish needs careful feeding. With the correct feeding discus should pose no problems. But having a different dietary tract to other fish, discus could be troublesome if given incorrect foods. Live foods can carry parasites, viruses or bacteria and pass on to discus and cause problems, with live tubiflex being the worse offender. Tubiflex worms are normally found living in drain systems and feed on the faeces deposited in them. Years ago this type of food was thought to be ideal for discus, soon after problems were found evident, and the fish was blamed as difficult to keep when it all went wrong. Some old books still sold today show pictures of live tubiflex worms hanging out of floating depositors, leading new discus keepers to thinking this is the correct way to feed discus. The only live foods I would trust is cultured white worm, and brine shrimp. Brine shrimp is a good live food for discus, because any pathogens found in the live brine shrimp food will not survive long in fresh water, and cause no problems in fresh water. Frozen Beefheart mix combinations from a trusted source such as the ones on this website and a brand I trust and offer for sale ourselves at Plymouth Discus Products are perfect to offer in with any discus diet. Yes, discus can be tricky at times to keep and accommodate. But if they are kept within their correct conditions and requirements, they are not as difficult to keep to any other fish. One last top tip to consider when keeping discus is not to over crowd them per space offered, or under crowd. They are ideal in numbers of six or more, but please allow ten gallons of aquarium water per fish. This rule can be broken and I do it all the time, and if you do, make sure you step up water changes in line to compensate. Discus like it hot, and by keeping them at 86f / 30c your discus should not suffer any problems with parasites, because the parasites will not tolerate or like the higher temperatures. Just before I leave you all for my first Blog, here are a few more little tips to keep you going until next time.1 Wild Symphysodon Aequifasciatu green discus

1) Test your discus water every week, and adjust water parameters if needed.
2) Make sure if you use power filters that the flow out put is not too fast. Discus having high-sided bodies will not like being blown around by fast flowing water.
3) Make sure you keep other discus compatible tank mates with your discus. I have seen Frontosa’s and even goldfish kept with discus in the past years, which are not ideal.

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