I have some no more algae tabs that I use quite frequently in my tank while I am changing the water to losen up th algae on items in the tank and make it easier to scrub off. I usually have the fish out of the tank when I put it in there . well yesterday I put half a tab in as a presentative and came home to find one of my spotted cat fish dead at the back of the tank under the bubble wand. His barbells were missing and he had a red spot on the bottom of him. The other cat and my goldie are doing great. Have any of the rest of you experienced this?