ONE Cichlid for 55 Gallon?

I would go with a pair of fisg in a 55 gallon tank. The tank is good size to hold more than 1 fish. Id go with something like a pair of jack dempseys, or pair of texas cichlids, or pair of green terror cichlids, or 3-4 firemouths in it. Firemouths are easy to maintain, and are a simple solution to new commers to the cichlid community. My FireMouths are generally displayfull, they tend to show theyre colors quite well, and are trained that when i barely tap on the glass they know its feeding time.

So i would recommend a pair of fish at the least.
 
if i were going to do just one fish in a 55 it would not be an african. yes africans are awesome and some of my favorites BUT oscars rule. they have arguably more personality than any pet fish, you can buy them small and watch them grow to a span of 10-12 inches, and they are gorgeous. the beauty of keeping african cichlids lies largely in enjoying the variety of colors a number of them in one tank offer the aquarist. additionally, the interaction between a number of africans in a tank is a sight to behold as is the spectacle that can be viewed as a number of them feed at one time. with all due respect to your idea of having one african in a 55, i simply don't think you'll be happy with it in the long run. i equate it to buying a 7 bedroom 4 bath house to raise an only child in. if i want less tank maintenance and one african, i'm putting it in a 10 gallon tank, not a 55. i may have less bio load in the 55 and therefore less frequency of water changes needed, but it is going to have to be cleaned eventually........ all of it. and like the 7 bedroom house with 4 baths, i'm going to get pretty darn tired in the long run cleaning that whole space when i could be in something 1/4 the size. ok, i have way too much time on my hands. this post is way too long, but you more than get my point by now. i just don't want you to be unhappy in the long run.
 
I wouldn't do a front trio in a 55 for life. Males can and do reach 14" and the females can still get over 10"...and fronts are a pretty deep-bodied fish as well. I'd personally get a wet pet like a RD/midas or a nice hq fh.
 
What about a nice male EBJD? Not much can rival them visually from the CA world.

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