HI BW, welcome to AA.
Well, in my redneck terms, there's two kinds of cloudy water. Mineral borne and critter borne.
The mineral borne can be dust from substrate or filter packs not rinsed enough. Things to try are 1. make sure filter(s) are clean and have good filter pads and flow. 2. Put in a finer "water polishing" pad. 3. For really fine suspended solids, try a flocculent like API Accu-Clear. It makes the fine stuff clump together so the filter can get it. It will cloud your water even more at first but will clear by overnight.
The critter borne can be bacteria from tank not being through its Nitrogen cycle. Test water and make sure your're not in a mini-cycle of elevated ammounia & nitrite. If so, do a 50% water change and test again in 24 hrs. Also critter borne is an algae bloom. Can be caused by lights on too long, low nitrates & high phosphates & infrequent water changes. Dying plant matter and overfeeding can make bacterial & algae blooms.
Corrections to this- try less lights-on period, water change, put a Seachem Purigen packet in your filter or Fluval Clear Max packet. (Be sure and prerinse them WELL) also investing in a good UV filter helps alot. I'm sure there are other things that many know about, but these are the first basic things to try. Hope this helps. Look through alot of the old threads in here. There's many about algae and cloudy water. Good luck, OS.
