History, Varieties Available and Optimum Water Conditions
Discus - perhaps one of the most intriguing and revered species available in the hobby. Even though the Discus is now bred successfully by quite a few hobbyists in this country, anyone who can keep them alive and growing is generally regarded by fellow aquarists as someone a bit special. The aquarist who not only keeps them thriving, but breeds Discus as well, assumes the mantle of a 'super being'!
Why should this be so? Discus, like marines, require optimum water conditions. If correct aquarium husbandry is applied, there is no reason why anyone should not be successful with either Discus or marines. In this article I hope to pass on to you some relevant information regarding the former, which will enable you to join the elite!
However, more about water conditions later. First of all, let us have a look at the fish themselves.
Discus fish are so called because of their shape, like an athlete's discus positioned vertically. They belong to the family Cichlidae and are thus cichlids. Cichlids are extremely diverse with many genera. The genus we are interested in is Symphysodon, which literally means "having teeth in the middle of the jaw".
The first Discus was Symphysodon discus heckel, which was described by Dr. Heckel in 1840. It is also known as the "True Discus", not for any reason other than it was the first of the genus to be discovered. This fish is different from other Discus in that three of its nine vertical bars are more prominent - the one through the head, the fifth or middle bar and the caudal or tail bar. The fish is also covered with wavy blue markings on its flanks. S. discus emanate from the Rio Negro and its tributaries, itself one of the tributaries of the Amazon.
Symphysodon aequifasciata aequifasciata, better known as the Green Discus, and described by Pellegrin in 1904, was the next member of the genus to appear. They are found in Lake Tefe and Peruvian Amazonia. These fish were then really almost forgotten until the mid 1930's, when they were introduced to the hobby. Once their exacting requirements were realised, spawning began to be observed.
Quite rightly, Discus were known to be closely related to the Angel Fish (P. scalare). It was therefore assumed that their breeding requirements would be the same, i.e. remove the eggs, hatch them in a separate tank and grow the fry on. This, as we now know, is not possible with Discus. Discus fry, as a first food, consume the mucus excreted from the flanks of the parents. Discus were not therefore successfully spawned until the late fifties with Jack Wattley in America and Eduard Schmidt-Focke in Germany doing the pioneering work.
In 1960, Schultz described two further sub-species of Symphysodon aequifasciata :- S. aequifasciata axelrodi, the Brown Discus from Belem , near the mouth of the Amazon, and S. aequifasciata haraldi, the Blue Discus, which is found near Manaus in Brazil. Controversy still surrounds these classifications, with some taxonomists claiming only one species exists, the non valid sub-species being merely regional colour variations. I must admit to sympathising with this point of view, but then I'm not an ichthyologist!
In the last thirty years, many superb hybrids have been created by selective breeding in Germany, the United States and Japan. These fish are extremely expensive and highly prized. A breeding pair can be valued at thousands of Pounds, and most enthusiasts hope one day to own and breed "Brilliant Turquoise", "Powder Blue", or "Cobalt" Discus.
For the newcomer to Discus keeping, I would recommend the Brown Discus (S. a. axelrodi) which is now available relatively cheaply due to mass breeding in South-east Asia. However, beware small Discus with very bright red or blue faces, as this colouration is achieved by breeders in the region adding a hormone to the food which is fed to the Discus.
Should you be able to raise these fish to adulthood, they would probably turn out to be sterile. Not only that, but a much more rapid effect would be to see this "highly coloured" Discus revert back to being an ordinary Brown (S. a. axelrodi). The problem is that once the hormone supplements are withdrawn, the fish just returns to its normal colouration.
If finance is not too much a consideration, then the Blue Discus (S. a. haraldi) is a more colourful fish, with blue lines extending from the head into the flanks - the more lines, the higher the price! Do not be tempted by the Heckel (S. discus) as this fish is more difficult to keep requiring higher temperatures (90°F plus). It is better when some experience has been acquired.
Now to business! Discus being from the Amazonian river system, require soft, acid water. Unlike many other characins or cichlids from the same area, they will not readily adapt to hard alkaline conditions. Consequently hobbyists with these conditions will be lucky if the can keep Discus alive longer than six months.
I too have heard the stories about aquarists who have kept and bred Discus in water conditions more suitable for Rift Valley cichlids. If they are true I assure you that it would be the exception, rather than the rule.
Get yourself a total hardness test kit of a reputable make and see what your tap water provides:- 0°-4° dGH, ecstasy, draught Amazon, breeding a distinct possibility. 4°-10° dGH not too bad, Discus will thrive and may even breed, but adjustment will more than likely be necessary. 10° dGH plus, and you have got a problem! If it is any consolation, it is also my problem - water in the Bristol area, where I live in the UK, is 22° dGH which is more like draught Malawi!
If you have hard water, how can you get around this situation? The cheapest way is to collect rainwater in a plastic water butt. Avoid metal guttering and do keep a close fitting cover on the butt to eliminate unwanted insects and algae. It is also probably a good idea to fit some sort of strainer over the down-pipe to eliminate larger debris, like leaves. Do not forget to clear this strainer regularly, however, or obviously not much water will reach your butt!
Prior to using this rainwater, I would recommend that it be filtered through a good quality activated carbon. This medium will absorb most chemical pollutants which the rain may have picked up on the way down. Pay particular attention to this if you live near an industrial complex.
If rainwater collection is impractical, the only other real alternative is to use deionising resins which, put simply remove magnesium and calcium carbonates and sulphates from the water.
DO NOT use a domestic water softener. Although these contain a resin which removes magnesium calcium cations, they are in fact exchanged for sodium ions. Sodium is an element in salt (NaCl Sodium Chloride), so obviously a sodium imbalance must be avoided. Two resins must be used, hence the two column deioniser commercially available for the purpose.
It is possible to construct your own deioniser, but the choice of resins is critical. And regeneration of resins can prove to be inconvenient domestically.
Having now obtained water of the correct dH (hardness), let us now turn to pH (acidity / alkalinity). As an aside, it never ceases to amaze me, when giving a talk to clubs and societies, how many "aquarists" confuse these two terms! Do not forget:- dH = hardness; pH = acidity / alkalinity. Discus in the wild tolerate a wide range of pH readings, from as low as pH 4.5 up to pH 6.8, but always an acid reading. pH 7 is neutral and any reading obtained above this is naturally alkaline.
Use a reliable accurate test kit to determine the pH of your tap water, then add a proprietary pH adjuster such as that produced by Technical Aquatic Products Ltd. or another reputable manufacturer. Do not overdose - read the instructions carefully and re-test the pH until the desired acidity is reached - ideally, pH 6 to pH 6.5.
Now that we have discussed the fish themselves and the water conditions required, join me next month for a look at the "set-up" itself, and the do's and don'ts of persuading your discus to spawn.
©Max Pickering 1999