I know this thread is a little old, but...I too have cloudy water in my 75 gal fowlr. I dont think it is an algae bloom rather I think it is just the fish, lunar wrasse in particular, dive bombing the sand a lot causing fine particles to free float. I also have a blue throat trigger, spotted puffer, squirrel fish and sailfin tang in the tank. I change 10 gal of water each saturday in that tank and the parameters are always good. What can I do to combat this? Or do I just have to suck it up? The tank was always clear until I added the wrasse two months ago and then it started to get a little cloudy, not too noticeable. Once I added the puffer and trigger it got worse. The trigger hits the sand a lot also.
The sand is really fine sand. Should I change the substrate to something different? If so, how do I go about doing that?
Thanks,
Mark