If the small plecs are
Hypostomus punctatus or
Pterygoplichthys pardalis they are 'common' plecs and get very large over time - to over a foot and a half. Find out what they are.
As regards malawis you can certainlly have some more. The mainganos are the ones to watch as regards aggression - don't put similarly coloured fish in with them and you should be ok. Both the acei and the labs are quite peaceful for mbuna.
In your tank I would increase each of the 3 groups by one or two fish. Ideally increase the acei and labs to above the mainganos as those are your two less aggressive groups (also the male/female colourations on these two are equally attractive/identical). Keep the ratio at 1 male to 3/4 females.
I think you can then also have either but not both of :
- one more group of say 4 mbuna (one male and 3 females). You might like iodotropheus sperengae (rusty cichlid), or pseudotropheus socolofi (nice powder blue, also comes in albino if you like white - would look quite cool
with your mix).
- a group of male aulonocara 'peacock' cichlids - say 1 each of 3 different species. Would be very vibrant and colourful. Be aware that a number of very respected keepers of rift lake cichlids reccomend strongly that you do not mix aulonocara and mbuna in a tank of your size. However, factoring in that you would not be mixing male/female and hoping to breed etc. I believe you would be ok doing it, subject to the general rule with cichlids that there's no accounting for individual 'personality & character' (i.e. murderous intent lol).
Finally I stress that you need to work out what the plecs are. Try
www.planetcatfish.com and check out the names I gave you. If they are commons I advise moving them now before you get too attached. Replace with 2 synodontis catfish or one bristelnose plec.
The guppies woujld also be far, far, far happier out of that tank.
Hope that helps
