Post #60812 by laney on Wed, Nov 19, 2003 9:48 AM

I have had repro mugs in my tank through fresh water tropical fish (they'll hide in them) to my larger koi tanks. They have never been a problem. The only thing I suggest is fill them with rocks when you sink them, even if they are on their side. Dirt will settle in them and it will keep the fish from hiding too much. They also make a safe cave for cray fish, who will clean some of the settled dirt, etc.