Looks like I have dandruf in my tank

Question
 About a month ago after I did a 20% water change and some cleaning in my tank I noticed some stuff floating in my water that looks like white dandruff.  I have a 30 gallon saltwater tank with about 20 lbs of live rock and I also have live sand. I have a emperor 280 h.o.t. filter, a remora c protein skimmer and an 8 watt UV sterilizer running in the tank. My filter and UV sterilizer don't seem to be fixing the problem.  
    The one thing that might have happened is I accidentally left some R.O. water that was mixed with salt in the container that I use to refill my tank.  This water would have been sitting for about 3 weeks or so and not thinking I added more water to it without emptying the container and rinsing it out. Any idea how I can fix this situation.  It doesn't seem to be getting any better.

Thanks...
Chris

Answer
Hey Chris

That dandruff is weird. it could be a few things. Do you for sure watch that all the salt gets mixed in when you make new water? if not, it could be loose salt crystals floating around. if thats not it, what food do you feed? make sure all the food gets eaten, the white could be decomposing non-eaten food. if it doesnt sound like one of those, check if your HOT filter is spitting out some fluff, canister filters and hang on canisters like the HOT are known to do that. if it doesnt sound like its one of these, feel free to send me a follow up