Pretty much any tank is big enough for an eel, the size isn't the problem with them. Some of the problems are....
1. As they grow, they produce a ton of bioload on the tank. The smaller the tank the higher the need for very good filtration to remove those wastes. The filtration also should include a lot of biological filtration to break down the ammonia(and lots of it at once when it poops) into safer compounds like nitrate. Then water changes to remove the nitrate.
2. In tanks that small, you can't really keep other big fish because there isn't enough space for them to swim around. You can't get small fish either, because they can/will get eaten by the eel. It leaves a pretty boring tank IMO because eels don't come out of the rockwork much at all unless it's feeding time.
Side note, make sure you get glass covers for an eel tank. They like to jump.
They stay a good size as well. I have not seen any over APPROX 24 inches at all in LFS.
Pretty much any tank is big enough for an eel, the size isn't the problem with them. Some of the problems are....
1. As they grow, they produce a ton of bioload on the tank. The smaller the tank the higher the need for very good filtration to remove those wastes. The filtration also should include a lot of biological filtration to break down the ammonia(and lots of it at once when it poops) into safer compounds like nitrate. Then water changes to remove the nitrate.
2. In tanks that small, you can't really keep other big fish because there isn't enough space for them to swim around. You can't get small fish either, because they can/will get eaten by the eel. It leaves a pretty boring tank IMO because eels don't come out of the rockwork much at all unless it's feeding time.
Side note, make sure you get glass covers for an eel tank. They like to jump.