Saltwater mixing tank

[4everwet]

I have been using a 40 gallon poly tank for mixing saltwater in and it starts to get some weird brownish film inside. Could it be because the poly tank is clear letting a little light in? Would I be better off with a brute trashcan since it is opaque? Any help or suggestions greatly appreciated!

[frederickk]

I would go with the Brute one as they don't get that brownish colour when you use it.

[crabbejoe]

Could it be diatoms?

[frederickk]

In the bucket? i would doubt it!