serpaes are nice, you could also go with a bigger school of little tetras or rasboras. in the long run though your leporinus will get big enough to eat a lot of smaller tankmates so serpae sized tetras might be best. I agree with candycat- leporinus get really big, I have actually seen one that was around 19", but a foot is definitely standard. I woudl think about rehoming him or getting a larger tank. What kind of pleco do you have? they can get big too. clown loaches absolutely get too huge for your tank. If you like loaches you might try some of the smaller botia species like yoyos. But if you do go for long finned fish I woudl avoid botias.