i sent this to amazontanks a while back about her 55 gallon mbuna set-up, hope it helps.
in a 55 gallon you can do a killer mbuna (rock dwellers) tank, or you could do peacocks (very pretty) or other haps.
in a 55 due to the size of the tank, i would PERSONALLY do an mbuna set-up.
i will break this down in every aspect i can think of for you:
1st thing: in the bottom of your tank (bare bottom) you should put a layer of eggcrate (cheap at lowes or home depot in the lighting section -also called fluorescent ligting diffuser) which will allow you to put a heck of a lot of rockwork in your tank without having to worry about pressure points and having your tank crack in the bottom.
substrate: if you look at pictures of lake malawi and tanganyika you will notice that most of the lake bed is covered in sand. if you want the full range of natural behavior from your africans i would recommend some type of silica (which is inert) sand. the kind i like comes in a 50 lb bag at Lowes for 2.39$ -- it is called "medium- coarse" quikrete sand. it looks awesome and works great. 1 bag o this would do your tank just fine.
many people like to use crushed coral, or aragonite, crushed oyster shell, or some other type of so called "buffering" substrate. i dont feel that these look as good nor do they really "buffer" the water....especially since my water is already pretty hard. plus--crushed coral is a real pain in the ass to keep cleaned. sand is VERY, VERY easy to keep cleaned.
what is your ph, kh, gh ??
my advice is to go with the sand, it is the best.
filtration: i imagine you already have filters, but if you plan to use sand as your substrate i would recommend a canister over a HOB as your canister can suck up a little sand without buring the impeller up.... which really sucks, trust me. if you cant get a canister filter, you should really cover the intake pipes of your HOB's with a piece of sponge and raise them fairly high in the take to prevent (if at all possible) sand from getting into the filters.
decoration: for the most natural mbuna tank possible, i like to use "roundish" chunks of granite or some other type of rocks. the way that you place them in your tank does NOT matter, as the fish will pick caves and hiding places that you NEVER thought possible....trust me. if you design the rocks with the "idea" about where caves will be the fish will not use them--they will make their own. so i just make little piles and let the fish have at it!
NOTE- many people LOVE to use flat rocks like slate, which look like crap to me. they stack these slate rocks with silicon and fill their entire tank with them and i just cant stand it! you find NO flat like rocks in either of the african lakes!
now for the fish:
species i think are more trouble than they are worth
- melanochromis auratus
- maylandia lombardoi (kenyi)
- maylandia crabo (bumble bee)
- pseudotropheus demasoni
all of the above are either too aggressive, large, or try to hybridize with everything...just say no to them.
species i think are great:
- labidochromis caereleus (yellow labs)
- Iodotropheus sp. (rusties)
- zebras
- Pseudotropheus salousi
- P. socolofi
there are others, but these are my favorite
you could make a nice tank with only a couple of species (regardless of what other people tell you)
in all honesty, if i had to set-up a 55 gallon mbuna tank, i would get these:
6-9 yellow labs (they play very nice together)
3-4 rusties
maybe a couple of cobalt zebras
and that is about it!
i prefer few species, many of them----rather than what a lot of people do: 1 zebra, 1 auratus, 1 socolofi, 1 rusty, etc. which is boring IMO.
HTH--keep me posted,
M
eggcrate is cheap and is a good insurance policy for your tank.