Here's a thought! Although you know you can't care for sweet fish (all small fish do in fact suck) in a small tank - try a juv. trigger and an eel. They are extremely hardy and will be rewarding to keep -- until you MUST move them to a bigger tank or get rid of them. The way I look at it is, if you can provide a fish a good home for a while, even if it is only a short while, you will have enjoyed that experience and the fish will be happy too!
Nobody can provide some of these fish the homes they deserve eventually, IMHO, so at whatever point you can do it, do it!