cloudy water

[Jnicho]

Old sand and tap water fueling free floating algae bloom would be my guess. Stirring up a sand bed can be a mess and almost all municipal water has phosphate added to it to inhibit corrosion. Your water tests negative for phosphate because the algae are using up as much as they can get...more phos=more algae...less phos=less algae...an RO unit and good skimmer are the 2 most important items in this hobby IMO. I would HIGHLY suggest spending the $$$ on a decent RO unit.

TDS=Total Dissolved Solids...or the junk in tap water that will fuel algae growth as far as our hobby is concerned. Water sources can be tested for TDS to see how "clean" they are...Most people who run an RO unit also have a TDS meter of some sort...it's the only way to really tell that your RO unit is working correctly and when it's time to change filters/membranes.

[Jadinop]

It could also be a bacterial bloom. If the water has a white cloudy look to it that would be my first guess. Whether it is an algae or bacterial bloom if you can buy or borrow uv sterilizer that would clear it up pretty quick. The floating algae/bacteria blooms are harder to clear up than your usual algae problems.

[reefqueen]

that was my next plan of attack...i have a uv but i havent used it in about a year so i'm going to get a bulb for it

[ScruffyRubicon]

Originally Posted by Jadinop

It could also be a bacterial bloom. If the water has a white cloudy look to it that would be my first guess. Whether it is an algae or bacterial bloom if you can buy or borrow uv sterilizer that would clear it up pretty quick. The floating algae/bacteria blooms are harder to clear up than your usual algae problems.

You beat me to it! I had this happen to my 12g nano shortly after I set it up. I did a large water change (more than half) and all was good the next day.