look the problem is , there is not really anything to suggest for a 55gal that will not eventually outgrow it , or become aggresive toward your other fish in central or south american cichlids that is also very bright and colourfull . the few that would poss work have allready been sugested . something along the lines of a texas cichlid would probably suit you but not your tank . even outside the cichlid group there is little choice that would suit all the contitions of your tank .
about the lighting , it does make a diferace as some fish will look stunning under natural light conditions and yet some will not look how you want , even though they are colourfull in the shop . a fish with a reflective scale will look much better naturally light from the side or front of the tank .
the best thing i could suggest keeping in mind you specified requirments would be something along the lines of something from the acara family ( poss Geophagus heckelii) or one of the smaller south american such as nannacara anomala , you could try a small central american such as cryptoheros sp. red point but even them may bully some of your other stock and i fear they will not be the brightness and colourfullness you are looking for .
thing is nothing is going to compare to a ebjd , there is no other non african with such colour that will go in your tank. but then even if yours had survived it would of caused problems down the road anyway as they are quite a feisty fish and grow quite large . i know you did not really want to go with anything from the african lakes , but i feel the fish you would be happiest with would be found here , forget about the every day mbuna and look toward a colourfull hap or peacock as your centre peice something along the lines of a taiwan reef or a male aulonocara , add in a bit of coral or tuffa rock to harden up your water a bit and it would show great colours under natural lighting. its the only thing i can think of that would replace a ebjd in terms of colour
cheers col
