I have a 30gal with 4 africans(red top zebra, johanni, 2 OB haps) and 2 americans(convict, salvini), I m having a lot of problems with it, please advice me what can be the best among the two options: Removing all the Africans and the Salvini, and adding a Firemouths with a school of tiger barbs or removing the Americans adding more Africans(coz they do well in crowded crowded conditions) with a Fluidized bed Filter(not necessary for small tanks, I consider it handy in crowded African tank) to take up the heavy bioload. In this case what other Africans to add and how many of them?