I live in Houston TX and when temperature hit > 100 F all my gold fish died. I have about 60% of the surface covered with plants, and I even installed a tent over my pond, but it did not help. I tried additional aeration as well. The water temperature reached 95F and over several days fish started dying. The algae bloomed and it did not help the quality of water in the pond. Nothing seems can be done when the surface is exposed to light, even not a directly. The pond size is 1200 gal. Anyone can advise what I could have done?