I asked my husband about your guy and he informed me that they get to full size anywhere between 18 months to two years. So 4" in 6 months is not really that bad, he still have a lot of growing time left.

As for the air pump, he did say stay small so that the it does not make any big water movement, but it is important that they have it. He said if you are handly maybe you can make something that slows the flow down. Or maybe get one of those min-filters that they came out with for 1 or 2 gal tanks.

A little trick that he does with our fish and for the ammonia sense we are not fatefull on testing also. We get the little white ammonia rocks that they sell for goldfish and put one or two in the tank. just wash them first. It really does help alot at least with us. We have never had a ammonia poblem and our guys are doing so well that they are breeding like rabbits. So much so we are now up to 5 tanks and still have enought to supply out local pet store with african Chiclids. Just a thought for ammonia.

Hopefull someone else can help you out also and give you other ideas. Good luck with you guy.

BTW: what color is he/she? I saw a pink one awhile back ago and he was so cute, I almost got him, but we have no more room for another tank. I'd have to move out first.