I had a terrible day with all 20 of my cichlids dead. My tank and the inhabitants have been with me for a year and a half now. Last week when I went to my parents place, I noticed a wet area behind the house with lots of algae on rocks. It was like a velvet sheet( like Christmas moss) and somehow made me think it would look good inside my tank. I put it in the tank in the night and early morning everyone looked fine and enthusiastic as usual. Came back from work in the evening and everything dead. I suspect the algae had started growing in the presence of lights(mine is a heavily planted tank) and released toxins.
Does anyone know about algae being toxic to fish? I had the most beautiful African cichlids and they are all gone now. I know it was a real bad idea to introduce terrestrial algae in my tanks, but I had to learn it the hard way.