Stocking Up A New Discus Tank

Stocking Up A New Discus Tank

So you have decided to buy a new tank and you wish to keep discus in it. So how do you mature the filters And how long before you can add your discus stock.


The first thing to consider before you even buy the tank for your new discus is how big it needs to be. You will need to allow ten gallons for each discus. Also discus being a shoaling species a minimum number of at least six discus will need to be kept.
So with this information so far we can see that a tank of at least 60 gallons will need to be used for keeping discus. The only exception for this is if you have a bonded breeding pair. Even then it is very wise to place the pairs in separate tanks along side each other so they can see other pairs in the neighbouring tanks. Time and time again I hear of small tanks being used for keeping discus and two or three small fish being kept and then the keepers reporting that the discus are shy, hiding away, turning black or not feeding. Small discus especially will sulk if not kept in numbers of at least six, the more the better. Larger ones tend to not be so bad if kept in small numbers but will still need to be kept in good numbers for best results. I have always found that the bigger the group the less squabbling and fighting there is.


With the tank size determined and stocking levels planned how soon can you add your new discus Time is the key word here, because this is what you will need to mature and colonize the new biological filtration system. This is a very debatable area as it is possible to cheat here and I myself have had to do this in the past to get tanks up and running as soon as possible. Being a retailer time is also important and the sooner the tanks are running the better. Ways of speeding up the maturing process are numerous, some to name a few are placing mature filter sponges from old tanks, and then these can be squeezed out into the newly set up tank. When this is done approximately 95% of the beneficial bacteria is washed out into the new tank and is consumed by the newly running filters onto the new media, and hey presto. A good start for a breeding ground for the new colony. Other ways can be done by siphoning off dirty water from a mature under gravel tank and then adding the water to the new tank. Also good additives can be bought in a bottle to colonize the filter. But the best way and the old favorite is doing it like this. First set everything up and fill the tank with treated tap water or better still use an RO unit or water purifier and run the tank for 24-48 hours. Ammonia or waste fish products will need to be present so the cycle can begin. It would be no good running a tank with nothing in it and then adding the discus after weeks or months. Because ammonia would go up which would burn the gills of the fish which could make them dash about and may even cause disease or even death.


The best way to stock a new tank for discus is to set everything up, fill with treated water as described in step two. Add stress zyme or a similar product to help keep down the ammonia levels, protect the fish and help the maturing process. First buy a small group of tetras and add to the tank. Over the weeks increase the size of the group and if you want to add different ones like cardinals, neons, glow lights, rummy noses etc.Keep a good check on the ammonia and nitrite levels, if they rise do a water change to help the new filters. When you see a rise in nitrate you know that the new filter is working, i.e. ammonia is being broken down into nitrite and then into the third less harmful nitrate. Water changes on a regular basis will help to keep down the nitrate. As you build up the stock keep an eye on PH, as with the stocks growing waste products from the fish will make the PH drop so may need buffering up. After a week or so bottom small feeders like Corys or L plecs can be added. These are ideal as a cleaning gang to clear up after the messy discus. If after 6-8 weeks it is possible to add some discus, if all water perimeters are correct.


This may sound not so important but how you add your discus is very important. Many think it is good to add a few discus and slowly increase over a period of time. Unlike the tetras it is a good move to add at least six discus at the same time. The reason as already stated is the problems with discus in small numbers; also if you add them at the same time they can sort out a pecking order and settle down. If you add more at a later date you may have problems settling in new comers with a group already established.


    • PH: – 6.3 – 6.5 CAN BE AS HIGH AS 7 FOR SMALL DISCUS.
    • KH: – 3-4
    • GH: – 3-4
    • TEMPETURE: – 86
    • TDS: – AROUND 125


It will take at least six months to fully mature a new filter system. Stocking with smaller discus will put less of a strain on a newly set up tank. Because discus need temperatures up in the mid 80s make sure you have plenty of air stones. (High temperatures = less dissolved oxygen levels) Do not use bright lights unless you have floating plants, discus like subdue lighting. Make sure you have good tight fitting covers on the top of the tanks. Discus can jump out of tanks very easy.

Think T.I.M.E.

    • T. Is for time, taking plenty of this will insure better success.
    • I. Is for invest in the best equipment for your discus.
    • M. Make sure you keep a check on water quality.
    • E. Enter discus specialist shops only, they will be able to help if you have any problems or questions.

Chris Ingham

Author of Discus World, the complete up to date manual for the discus keeper.