Originally Posted by fish5
The clown loaches I have do NOT get huge like most peoples. At the store on the shelf it said these get up to 1-2 inches. The guy that works there also said that. Here is where I got them and it says 1-2 inches. I got the tiny ones. Exotic Aquatics :: Freshwater Life :: Loaches
I checked this link; this is how retailers sell fish, they indicate the current size because with some fish the size dictates the price. As an example, if you buy neon tetras when they are small, you might pay less than a dollar; but if they are medium size, they might sell for $2, and very large neons (full grown) will usually sell for more, say $3. It has nothing to do with how large the individual fish will grow, just the size at which they are selling them. The price difference has to do with how much it costs them to maintain them, and the survival chances (larger fish tend to survive better than fry).
As for the clown loaches, they are 12-inch at maturity. When large fish are maintained in less than adequate sized tanks, they do not grow properly. They develop internal problems, often with the immune system. They are under continual stress due to the water conditions. It is not so much the "size" of the aquarium that is the problem, but the condition of the water. In a smaller tank the water deteriorates more rapidly due to the biological processes of the fish and these processes increase as the fish ages even if it remains stunted in growth size; the internal processes are still "growing", hence the organ problems. If the water could be changed every hour or two, a larger fish would 'survive" in a smaller tank. But the space causes other problems then.
People in pet stores sadly do not always know much. As suggested in previous posts, research your fish before you buy them. A concensus of opinion on fish size indicates the information is probably accurate, and as noted every website will tell you about clown loaches growing to 12+ inches. Keeping these fish in a 30 g tank is not healthy and frankly cruel. It is like keeping a golden retriever dog in a 3x3 foot cage; it will "survive" but hardly "live" in such conditions.