I just got back from my lfs where I had my water tested. I do my own API testing but had a mystery of unexplained deaths so thought I'd double check my work. Kid didn't remotely do the nitrate test right and was happy to announce I had 0 nitrates in my tank. It's water change day and I took that sample before I performed the pwc. My test was 40 nitrates. That's really neither here nor there. What surprised me was a PH of 8.8 in my 20 gallon long with 3 black skirt tetras, fake plants, and the same decor that's been in the tank since start up. Until today my PH has always been 8.2 and that's what it is out of the tap. Since I got this freaky reading I came home and tested all 5 of my tanks. In the 2 2.5 gallon betta tanks one was 8.8 and the other was 8.4-identical set up but one is a little warmer than the other. My 20 gallon was at 8.2-8.4 My still cycling 29 gallon was 8.4-8.6 My cycled but as yet unoccupied 30 gallon was 8.2-8.4 Tap is 8.0-8.2, GH 7 and KH 10 (can't remember what that comes out to in ppm) Every tank except the 2.5 gallon ones have had pwc today. Any suggestions as to what could be causing my PH to climb so high between water changes? Can I even keep fish with a PH this high? I'm not interested in live bearers. If you've made it this far thank you.