My wife and I converted our 30 gal. tank to a 75 gal. planted tank 2 months ago. I check chemistry every 2 or 3 days and had no spikes. We were conservative adding fish. Current population: 6 med. rainbows, 7 sm. tetras, 2 sm. flying foxes, 2 lrg. angels, 1 med. red tailed loach, 2 sm...