I feel like I've tried everything under the sun to get rid of green, slightly cloudy water in my hot tub. Water seems to be clear until I add in (Frog brand) bromine and minerals cartridges. I've had the company who sold me the hot tub come out twice and they said the water was fine or that they'd fixed it, but it remained green and cloudy. I've shocked it repeatedly, emptied and refilled it three times (scrubbing and soaking the filter each time), tried metal remover, tried Brom Start and (after switching to chlorine), sodium dichlor. Hot tub is covered, and after last two empty/fill cycles was not entered, so it's not something we're bringing into the water. I've tested for copper and iron (both were fine). Any thoughts?