Just listen to Artesia lol. Good advice. When I totally re-did my tank with new filters and all, I popped in 2 bags of purigen and put in 2 UV Sterilizers and BAM that water was crystal and I have never had any cloudy or foggy water at all since October when I did my remodel. I find UV Sterilizers are good for any tank, even though they are recommended for an algae bloom, i have two running in my tank and what they do is kill all the little microscopic bacteria and parasites and junk in the water column and spit it back out into the tank. Keeps the water clean and clear haha. Purigen also is the best thing to put in a cycled filter if you want good water qualitiy.
Yup, stay away from everything except Prime - tha is the only thing I put in my tanks other than the fertilizers!