We are struggling with our 75 gal, open top, freshwater aquarium since moving 6 years ago. We've had discus tanks for 20+ years and had no problems until we moved. We currently have 3 discus, 4 cherry barbs, 4 tetras and a few cory in a planted/substrate tank with a Fluval FX4, LED Halo lights and we RO our water. Plants don't grow and we have constant algae. I'm not a chemist and don't care to be one so this is my last shot before selling the set up. Our water is very hard which is why we were advised to RO our water. This process has really hampered our ability to do water changes as our water can't be run/exchanged through the hose. We have to wait for the RO water and then heat up on stove to put into the tank that we run at about 82. GH is at least 180, KH less than 40, PH 7.0, Nitrite 0.5 and Nitrate 160 (which is probably the algae promoter). Advice??