I have a 310 gallon Planet Aquarium with 1/2" thick glass. I am using 4 MP40s on the tank and the tank has been set up for about 7 months. Everything was fine for the first 6 months, but over the past month, 2 of the MP40s have come off of the tank. The magnetic bond seems quite strong; so I am not sure why this has happened. Both occurred over night (about 2 weeks apart) on the same side of the tank. All has been fine though for the past week. The MP40s did come with "thickness spacers" that are for thick - for use with glass thicknesses over 1/4" and up to 1/2". Not sure if I need to use these spacers, if they will help or if they will cause the problem to occur again. I do have the dry parts somewhat secured to the outside of the tank with suction cups, really used to secure the wires and to keep them out of view as much as possible. I do worry that if the wet part came unsecured and fell to the bottom of the tank, could the dry part, now dangling from the glass actually hit the glass and crack it or could the vibration do harm to the glass?? Since both of the recent occurrences happened at night while I was sleeping, I didn't know about it until the following morning. Any thoughts or feedback? Anyone else using the spacers and are these something that I should be using? Appreciate the feedback!! Thank you.