This fish can reach over 2 metres in length, but if you were to buy one, it would most probably not get a chance to grow at all. This is because it is a very specialised feeder. It cruises through the water with its large mouth fully open, Basking shark fashion, filtering plankton from the water. Which is the only thing it eats. In captivity it will eat daphnia and other small free swimming aquatic insects, But in vast quantities, more as it grows, winter and summer, Unless you can provide such food, by the bucket full, all year round, please don't buy this fish. Spectacular as it is..

The Sturgeon

The Wels Catfish

It is now illegal to buy one of these without a permit. But I have seen them for sale on many occasions. These fish are among the largest of all fresh water fish. They have huge mouths and will eat anything that fits in. They grow quickly, a 4" specimen introduced into a pond will easily grow big enough and quickly enough. To eat anything else sharing the pond, and this includes large koi. It is also illegal to release one of these fish into the wild, for obvious reasons. But unfortunately that is what happened to many of them once they had polished off the goldfish, that used to share their home.

The Arowana

Photo by: The Fish Addict

These fish are usually offered for sale at a very young age. They are mouth brooders, (unusually it is the male that does the mouth brooding). The fry are usually retained in the brood pouch until they are ready to begin feeding on there own. once the yolk sac is all used up. Unfortunately there is a practise of removing them from their parents to soon and offering them for sale, still with the yolk sac exposed. Even at this young age they are already 3". If they survive being caught and transported (if the yolk sac is damaged they will die). You will have to start feeding them on Small crickets and other insects. Flake food will not do, these fish are carnivores. And if all goes well and the fish survives it will rapidly grow (to about 15" in the first year) and eventually to 1.5 metres. As with the Red Tailed Catfish, if you have the space this species presents no other problems, But keep it well covered these fish can really jump.

The 'Dyed' Glassfish

You can easily see the artificial colour. Photo by: Morty

The Indian Glassfish, in its natural state is totally transparent. Unfortunately some of the commercial breeders exploit this, and inject them with a fluorescent dye. In an attempt to improve sales. It is an extremely cruel practise and will shorten the life of the fish. There have been various campaigns to get the practise outlawed but I have still seen them offered for sale. Apart from anything else the dye will only be visible for a few months. By refusing to buy these fish, you will be helping to stamp out this cruel practise once and for all. Because no retailer is going to stock fish that don't sell. Avoid this fish at all cost

If you can think of any other fish that should be on this list. Let me know and I will be only too happy to add them. So that someone else doesn't have to learn the hard way. And some poor fish won't have to suffer. I know I've said it before, but it is important, Please make sure you can properly cater for all a fishes needs BEFORE you buy it. Do your own research, just because a person works in a shop, doesn't mean they are experts, their job is to sell things. The list above, should be proof enough of that.