What is the proper PH for a tank? I know it somewhat depends on tthe fish, but for some reason my PH has been dropping. Started at 7.2 when I started the tank, and has dropped to 6.0 at this point. My ammonia levels are at .25 ppm, no2 at between 2 and 4 (a bit high), and my no3 levels are at about a 5. I thought the tank had completely cycled, and added moore fish. Got a spike of ammonia the other day, and now it's nitrite. This is alll before a water change, which I just did, today. I don't know if the other levels effect the PH. But it's been sllowly dripping for 2 months. I have 4 tiger barbs, 4 red tails, 3 bala sharks, 3 red tail sharks, a plant (don't know what kind) and 3 marimo balls. After all of that. I know I have to wait for the levels to calm back doown, but ph seems low to me. I see most people want it roughly at 7, mine is at a 6. How do I fix this?? Or should I?