Convicts would probably be the funnest to watch, but often you will need a seperate tank for the fry. I would stick w/ the sponge filters too.Haven't bought the tank yet just planning. I just want to raise some fish from fry. I've researched so far guppies, endlers the fry won't fit in their mouth, and convicts. The convicts look interesting because of their nutty personality. Do I need a sponge filter for the convict fry or could I just use a hob?