I had a weird one today. 2 days ago one on my turbos died. I decided to keep it in as one of my hermits already decided to eat it. But then this morning something was strange. All my CUCs were still and my clowns swimming at the top gasping for air. Corals doing fine but got this weird feeling my tank was crashing. I tested the water and all ok but something was clearly off. Decided to do a big water change and with that to also clean the gravel (lots of dirty water). I also removed some of the rocks inside to make more space and allow to vacuum the sand. Now tonight will add some more water and clean the canister filter.