Bacteria bloom in fresh saltwater?

[BJanecka]

I've always made up fresh saltwater in my Brute and let it mix for 24 hours via a powerhead and used it. I recently mixed up a batch (18 gal) and had it circulating in the same Brute can for 6-7 days. I turned the powerhead off and noticed a short time later a film on the water surface. I guess it was some type of bacteria bloom that was happening in the water and the powerhead kept it stirred up enough that I did not notice it. I would think with RO/DI water (TDS at 1)and new salt (IO) that it would take longer for this bloom to get going. Has anyone else noticed something similar when allowing fresh saltwater to mix for about a week or so before using?

Brad

[duc]

I have had the exact same exp with IO salt, not saying it is the salt because I have had it happen with Oceanic also.
Clif

[GaryP]

I think its some sort of insoluble silt or dust. Bacteria wouldn't be floating on the surface. A lot of the materials they use when they make salt can have insoluble residue in them. Bacteria like to attach to surfaces like the sides of the container and wouldn't necessarily be at the water surface.

The other possibility is the stuff you are seeing is good old Calcium Carbonate. The buffer in the salt is not real stable and over a period of time the water will pick up CO2 from the air that can further destabilize the calcium/buffer equilibrium. I've noticed a lot of scale formation in salt that I have stored for more then a few days. Kalk will do this too. Kalk often has a "scum" floating on the top which is calcium carbonate formed when the Kalk reacts with CO2 in the air.

[Isis]

My thoughts exactly Gary.

[GaryP]

My thoughts exactly Gary.
I average being right about once a year. I guess I was overdue! :)