I just want to get this out first. Why are magnetic tank cleaners so, so, darn expensive?!? Okay, I only have glass tanks and have been using one of those long stick things with the sponge on the end but it doesn't work well I guess because there's no leverage at the end. The other day, I found a couple of large Odysea magnets in my box. Tried to use them and they barely stuck together thru the glass. I cleaned all of the contact surfaces off and tried again and the magnets would barely stick and just float off. Happened with both of them. I went to the LFS and saw that medium to large magnets were at least $50! What the heck. Are these special magnets? I'm going to my local hardware store that has industrial magnets that are also encased in plastic except the sides that contact the glass. Then I'm going to use industrial Velcro and hot glue it onto the surfaces cleaning the inside and outside. Has anyone tried this and are there any opinions? Thanks, Ed.