Greetings all. So the past couple of months I've had issues with both my 125 and 210 FOWLR tanks. I've lost several fish in both tanks, but there were no visible signs of disease on any of them. Just rapid breathing and usually staying towards the top. I was advised that it was probably gill flukes because they can cause those symptoms. I treated it with Prazipro which as a side affect dropped my PH to mid 7's. So then I of course started adding PH increaser(balance but also seachem 8.3) which they did there jobs. But then the fish were still looking stressed and I had the water retested and my LFS found very high KH(over 300, 17-18) and I was told at those levels it can kill your fish. So after a couple of water changes I got them back down to around 11-12. So I went to back to my LFS to get a few fish since by this point I lost several fish and only had a few fish left in the 125. So I thought I'd try a small school of green chromis which I've always had good luck with in the past. And at first they seemed fine and they all ate. But sure enough with a couple of days I started losing them, and the couple I observed seemed to be breathing hard and staying at the top of the tank like my fish had before. I retested the water and the everything seemed to be fine ( PH 8-8.1, nitrate under 30, no Ammonia, no Nitrite, KH still in the low to mid 200's) so I had no idea except for maybe the tank still had flukes in it so I re-treated with Prazipro(didn't really seem to help). SO I went back and relooked at the test results from my LFS(it's the API aqua spin, they email you the test results) and I did see the Phosphate levels were high (3.8) which until now I never have really worried about unless it was a reef tank. But then I read some where that if your Phosphates are high enough it can also deplete the oxygen in your tank. Is 3.8 high enough that it will do that ?