Going from African Cichlid Tank to Tropical Community Tank.

Question
I have a 40 gallon tank in which I have four male cichlids: 2 Electric Yellow Labs, 1 Acei, and 1 Albino Red-finned Zebra (the bully). They are very skittish; they hide when I approach the tank, unless it is their specified feeding time. They are beautiful, but honestly, I'm pretty sick of their behavior. So I'm coming to the conclusion that I will expand my guppies from their 10 gallon to this 40, and add some more small, colorful things. Things which, in my limited experience, have proven to be more "friendly" toward me (i.e., not fleeing into the caves when I pass through the room).

My main question is, should I do a complete clean-out of the tank? Full water change, fresh filter medias, blast off any algae and "gunk" from the (fake) plants and sides, and then let it sit and re-establish for several weeks before slowly transferring over the Tropical fish?
Or, should I use the bacteria I already have, and just continue to treat the tank with normal water changes and the like? I use the same water and conditioner, the same type of filter; the only difference is that the cichlids have an added pH buffer (which raises it to 8.3).

Also: I am rather attached to my Acei ("Monster"), who I raised from a tiny fry to his wonderfully robust year-and-a-half old self. I am wondering if it would be acceptable by him, and not considered silly of me, to want to keep him in a 20L tank, by himself? I have read that their minimum tank requirement is 29 gallons, but I just wonder if being alone makes a difference. I would be happy to supply him with his favorite cave from the 40, should you think it would make the move more acceptable.

Insight is appreciated in these two matters. And please feel free to accuse me of anthropomorphizing. I am sure that Monster would be okay leaving me for someone else's tank, but I feel a slight bond between us, and would like to see him through many more years if I can.
(I raised him in my guppy tank, when I assumed he was too small to hurt anybody; I was shortly proven wrong. Hence his name.
I actually got the other cichlids to keep him company- and they all ended up bigger and meaner than he was! Wouldn't it be gratifying to be rid of them once and for all?)

Answer
Hello,

I am Exp. Michael M. And I well be taking this question due to the late time of the other expert you have asked the question to.

The fish should do just fine if you leave the same water in the tank and just scrub the algae off. You dont need to do a complete clean out if there is not signs of a parasite or water conditions present in the tank, because they are both freshwater fish. Also Monster should do fine in a 20L tank. They tell you that they need 29 gallons but the reality of it is that if they are alone in a tank and have room to swim around good, then they will do just fine. For example I have a sixty gallon tank with two full size oscars (about a foot each.) as well as a jack dempsey ( a foot and a 1/4) and a pictus catfish (around 9 inches) and even a full size cati (around 1 foot.) and they all get along just fine. Especally sames it well be by itself monster should do just fine, And it would be a great idea to provide it the cave and a few fake plants!

So I would try and switch those tanks over whenever you feel like doing it. And they should do just fine. It might take them a while to settle with their new enviroment but they well love it.

If you have any further questions feel free to ask them

Thanks,

Exp. Michael M.