Discus fish are not mass-produced. However, every month several thousand young Discus fish are sold around the world, there are some basic rules must be observed by the potential purchasers.

Discus should be brought only where the purchaser can be sure that he receives the fish he is being offered. If he buys Turquoise offspring, Turquoise is what should be swimming in his tank a few months later. After all, there is no way of telling the potential colour of small Discus that is only six weeks old and 2 inches (5 cm) long.

It's also worthwhile to if possible to catch one in a net and hold it up against the light. Take a good look at it. Even at this early age, the colour of the scales will already tell you what morph you have.

Even small Turquoise Discus must show shimmering greenish colour. The true Turquoise sheen must be visible right across the body. Not simply the head colour but the whole body must be examined.

This method also holds good for large discus. As lighting plays an important part in the brilliance of Discus colouring, the existing colours will be properly seen when the fish is removed from the water. In another tank, under better lighting, a previously unremarkable fish will display its full beauty. The time of day and the condition of the fish also play a part. The fish are particularly good in the evening hours. They will also put on their full finery if they are healthy and feel at home.

Discus fish must be round. The correct body shape must be visible even in the young fish. Drawn out Discus will have stunted growth. This impairment supports itself in the form of enlarged eyes. If the eyes seem too large compared with the rest of the body, the fish has not grown properly. This will indicate an illness at some time and refused to take food for a while. This damage is already beyond repair. Even when very well kept, damaged fish will not grow back into shape.

However, the defect fortunately is not inherited. All that distorted Discus fish pass on to their offspring are their natural, inborn features. Damage caused by human hands during raising and keeping is not passed on to the young. If the offspring are looked after well, they will attain the normal sturdy Discus shape and differ quite clearly from that of their parents.

Many Discus fish have small holes around the head. Why this should be so is difficult to say. As Hexamita has so far not been discovered in Discus, we must assume that the holes are the result of attacks by a Spiro nucleus or other causes. Small holes the size of a pinhead around the eyes may be regarded as harmless and normal; they are probably a sign of aging, although such holes are found even in yearlings. Larger crater-type holes, on the other hand, are more serious. Discus with large, unsightly holes may be suffering from hole-in-the-head disease. If white lumps or growths appear in the holes on the head, the fish should not be purchased.

A further point that requires the attention of a Discus purchaser is the gills of the fish. Discus are prone from gill worms and other gill parasites. Fish infested with parasites or worms commonly breathe on one side only. This means that only one gill cover is spread for breathing. The second cover is held close to the head. Rubbing of the gill area against items of aquarium furniture also indicates infestation. Gill worms or parasites are a nuisance; they make life hard for the Discus. The problem can be cleared up with medications, but the new owner will have to spend some time treating the fish. This also presupposes that a quarantine tank is available, as the fish must first spend two weeks in quarantine before they can be put together with other fishes already present.

As the purchase price for Discus is generally quite high, the purchaser may be well advised to observe the fish at feeding time. The well-being of adult specimens, in particular, which may easily cost more than a week's pay, must be checked in this way.