In a 40gl tank you can get away with a few more of each but make sure they are of the same species. This will keep things uncomplicated. You could go for 1 of each color (since there are reds, blues, yellows, oranges, purples, etc.) but this type of show tank would be more effective if you stuck to only males of each species you chose and right now sexing would be almost impossible.
I wouldn't exceed 4 of each....actually, I quite encourage you to get 4 of each but not untill you're done with your cycling. This will help cut down on targeted aggression though you should remember to provide enough hiding places and possibly try separating territories by spacing one 2 or 3 piles of rock a few inches from eachother.
I also encourage you find your own rocks (if you can find them in your area) than buy them. Paying money for
rocks of all things is something I simpy can't fathom
. Perhaps if you wanted a certain look and/or had a particular taste for rock like Texas Holey or feather rock then by all means if you can afford it.
To prevent from introducing any nasties into your tank do a vinegar test (drop some vinegar on a rock and if it fizzles don't use it) and clean/scrub/boil rocks before you use them in your aquarium.
Sorry about MSN Messenger, can't use it on this comp.
Edit: Forgot about cleaners. For now I wouldn't worry about it. Many plecs put out more waste than they're worth as "cleaners" and commons get too big for a 40gl. Shrimp will be eaten, crays can be eaten or can kill your fish. An apple snail might be ok. I've had success keeping Malawi's and snails together but others have reported their snails losing their eyes due to curious mbuna or being killed and eaten by them. They also need to be prevented from being sucked into the filter's intake. Filter sponge tied over the intake works well but it's unsightly.
IMO if you really have a bad algae problem down the road or just want some type of plec that badly get a bushynose. Most species stay within the 4-6" range and are effective algae eaters.
Otherwise "cleaners" are simpy not necessary. Your fish should not be fed so much that there has to be some other fish in there to eat any leftovers and IMO these "cleaners" often go mistreated and misfed thinking they can live well enough off the leftovers of the tank's primary inhabitants. Any "cleaners" and bottomdwellers should be cared for, fed properly and be kept healthy as well as any prized show fish when in your care.
