I bought 3 new tanks and 3 of these magnents to ease the cleaning of the inside of my acrilic tanks .. but after first use on each tank .. unfortunatly I did not notice until I ruined all 3 .. there are scratches all over and now the new tanks look bad. I am a photographer and was hoping to get some nice shots after everything got going, but after trying to shoot anyway .. the scratches show up bad in the pics. I am researching to find a better way to clean these tanks and wish I had bought glass to begin with .. but the magnets say they do not scratch .. but they do!