Good move - wish I woulda chimmed in ealier but this good. The biggest problem you would've experienced was extremely high nitrates perhaps even nitrite as you had too many fish in what really is a small volume of water. Had you allowed that stock to remain you'd have created a bactreia-fungus-disease breeding ground as the fish got older and larger. Alotta your stock was fish that get 8" or larger not real ideal for a 12" wide tank and substandard filtration. Lotsa fish means lottsa water volume x lotsa filtration - biologocal, mechanical, and/or chemical.
When you upgrade to 300 gal you'll probably want a sump w/ 1 cubic ft of bio-balls and perhaps an algae scrubber - pre-drilled tanks will make your life with big tanks so much easier - at this point you can think numerous small fish or several large fish as it's pretty obvious you don't really understand how big some of these guys get nor their overly aggressive nature when breeding insticts take over. A full grown RD is a very robust 8+" and can be down right nasty. It will probably destroy every fish in the 55gal @ 1 year of age. This fish alone, will want all 4' of bottom room all to itself and kiss your plants, orinments and substrate good bye - he or she will dig it all up.
The nimbo(giraffe hap) was 100% male.
As for food - any good fish keeper will tell you a varied diet is best. Brine shrimp are good for the color Red as it contains Beta-cartine and also a good calcium source, vegatable matter is ALWAYS a good thing - the only life that can produce vitamin b1 (thiamin) is flora/plants - animallia cannot. B1 is most important for the building of healthy immune systems. However quality pellets usually have a scientifically designed mix of vitamins, protiens, and vegitable matter. Easiest way to tell if the pellets are of good quality is the 1st ingredient, if it reads anytype of wheat or wheat byproduct - not good, fish meal - good.
I've done numerous cohabs thruoghout the years - including mixing SA/CA's with mbunas, haps, victorians, vampires, cudas, wolffish, knife fish, arrowanas, sharks, brycon , chalceus, plecos, datniods, and bichirs. Some were a fabulous disasters others worked for years, some still do. There are some constants tho with SA/CA's the aggressive species are just that. If you want a tank with 10 fish gulping at the top of the tank and 1 fish swimming circles over his/her pit - keep blindly throwin' them in there. If not slow down - do research - learn how to control your water parameters and why. Welcome to MFK.