So my system is going into it's second winter in the greenhouse and last week when I went in to check on the fish and water levels, I noticed that the water is not looking good. It is a little brown and cloudy and there is some foam floating in the top of the tank. I can't do large water changes right now because the water coming out of the hose is super cold. Any ideas on what is causing this and what I should do? I have koi in the tank now and a heater that tries to keep the water around 70. I'm not sure how successful it actually is but at least they aren't freezing at night. I have a 150 gallon tank of water that has been left to outgas that I could use to replace some water. But when you have a 700 gallon system, I don't think it is enough to really make a difference in water quality.
PS I am in Boulder, CO and it is starting to get frosty here at night. Could the cold be doing this?
could it be protein in the water? overfeeding due to cold temps? bio-filter gone dormant and food not breaking down?
wish I could give you a real answer, but these are just my guesses for what their worth. :)