This is an odd coincidence! I joined this forum yesterday as I had, by default acquired an almost identical tank to this one. It contains 5 fish at present, I have no idea what they are, 2 are similar to the yellow and blue one mentioned in your set up and 1 is a similar shape but with grey sort of leopard markings, the other two are slimmer and yellow, black and white stripped. They all arrived yesterday with my son; he got them from a local pet store that had a big tank of Cichlids that included Firemouths in with what I believe are African ones. They seem very lost in the tank, which does have lots of hidey holes but from reading the start up article on this forum I am guessing it needs more fish. I am unwilling to go back to the original pet shop as clearly they have no idea what they are doing! The fish are all approximately 1.5” long The Tank is a Jewel Vision 190.