Hey y'all. This is something I've been struggling to figure out for a while now. I have a couple pearl gourmai in a 55g with 10 sterbai cories and 5 rummy nose (more on the way). It is a low tech planted tank. I run an air stone constantly and a Sunsun jvp-110 wavemaker the surface. I also have a Sunsun 304b cannister with a spraybar. The tank sits at 77 degrees. I mention all this because three times now my pearls will randomly start acting like there's no oxygen in the tank. The first time, I moved some plants and thought I stirred something up. The second time my wife noticed that they were acting funny and soon followed by the cories spending more time at the top as well. A 30% WC seemed to fix it, but time could also have fixed it. The third time was yesterday. I started with a plant trim, then a 50% WC. They were fine a few minutes after the change. I test water parameters every time this has happened, and they come out normal (0/0/20). My pH sits around 7.6 In terms of causes, I'm totally lost. I have plenty of ways to keep oxygen high. It usually happens once the lights are off, but I don't think I have enough to plants to suck up that much oxygen. One friend suggested Gill flukes. Could this be it? I have videos of the most recent episode I can load once I'm home. I thought maybe it could be a pH swing (my kh is nearly o), so I added some crushed coral to my filter, but it happened again. Any and all help would be greatly appreciated.