Here is something i would recommend to anyone who has a big tank with big messy fish, and cloudy water.
Laguna pond clear, yes i know it is for ponds and i know its a tad expensive but blimmen heck it works a treat.
The trick is to pack your filter with filter wool, put a couple of cap fulls in after lights out, and when you get up in the morn, crystal clear. The filter wool needs to be removed the next day though.
I say after lights out, cause once you put it in, your water goes like milk.
I have used this many times on my big tanks, and it doesnt bother the fish at all.
I have had the same probs with cichlids, ph probs and cloudy water, it takes ages for the tank to wear in, i suppose you could say.