[rjharper]

I don't get mold, but I do get a milky white sludge at the bottom of the bucket I keep it in.

[Thirsty_Monk]

I don't get mold, but I do get a milky white sludge at the bottom of the bucket I keep it in.

That is the indication of salts in the water reacting with StarSan. Use Destilled or RO water and it will go away.

[HoosierBrew]

That is the indication of salts in the water reacting with StarSan. Use Destilled or RO water and it will go away.

+1.  It's the one thing I use distilled for. My star san stays clear until gone, pH checked.  Up near a year.

[Stauffbier]

I use distilled as well. I've never had mold, or sludge, or any other strange stuff like that. I do get some lint in mine sometimes. I've been known to strain it with voile if I don't have distilled water on hand.