Helloelliee said:
Do yourself a favor and do as much research as you can before deciding what to purchase, including equipment, but in particular for fish. Avoid impulse purchases. Some will tell you that a 55 gallon will limit your selection of fish. Try to avoid mixing overly aggressive fish with less aggressive fish. I always look up potential purchases here
http://www.cichlid-forum.com/profiles before I buy any. However, I post all questions on this forum (that you are reading now).
The whole sand vs gravel in my opinion is largely personal preference. I have dark blue gravel in my 55 gallon and they seem quite content. However, some seem to like to see Cichlids root around in the sand and filter through it. I wanted less maintenance, so I selected gravel.
I found that with a 55, one side of the tank would be colder than the heated side. So I purchased a second heater to even out the heat, and to provide some redundancy in case one failed while I was away, etc.
Quite a few state that Cichlids are hard on plants because they tear around the tank, especially when they are mature. I went with artificial plants, just because I already had some. I've never tried live plants, admittedly.
Some (most) African Cichlids like/need caves and/or hiding places. Some folks purchase a considerable amount of stone and build up rock work, sometimes securing their structures with aquarium-safe adhesive. Personally, I didn't want to add all of that weight to the tank, and envisioned it blowing out the bottom. I'm sure I'm just being too paranoid, but nonetheless I hunted through the stores until I found lightweight alternatives. They really do like to have places to duck in and out of, especially if they are breeding. People say good things about Cichlid-Stones as well (Google).
Plan to do partial water changes at least weekly, and large water changes monthly. Opinions on the quantity and frequency of these changes varies widely. Just keep checking your water parameters to keep them in acceptable. More fish means more waste, which means more water changes. FYI, some Pet Stores will test your water for free.
Select good food. An overwhelming majority state that New Life Spectrum (either Thera+ or Cichlid) is the best thing for Cichlids. (BTW, PetCo sells NLS.) Other folks like Omega One as well. Stay clear of generic fish food, and keep the proteins low (Google Cichlid Bloat).
Lake Malawi Cichlids prefer hard, alkaline water. I always bypass the water softener when I fill the tank. If you have city water, you should consider adding conditioner remove Chorine/Chloromine before adding to the tank. If you have city water, post here to ask folks for their opinions on which to get. I have good well water, so I don't need it (in my case). Other Africans may require different water parameters.
So far as what species, select compatible species. Yellow Labs are great starter Malawi African Cichlids. They have a peaceful temperament, they are pretty, readily available, breed easily, and easy to care for. If you plan to buy your fish in local stores, see what they have, take pictures, write down the names, then go home and research them. Don't always believe what the local fish store tells you. Listen to what they have to say, but then post questions here to get verification.
BTW, when you add fish by degrees, don't wait too long between so that your older ones get much larger than new ones. Otherwise the bigger ones may pick on the smaller ones.
Enjoy!