Magnets to keep things in place?

I saw that my koralia pump was set in place by magnets. I had an extra pair of the magnets from another pump. I used the magnets to hold my in tank skimmer in place with success. I'm wondering if you guys think its a bad idea to superglue all other things in my tank to similar magnets. the suction cups for some of my equipment comes off easily. If i go with magnets, is it okay to use metal magnets or should I try to find plastic covered magnets? Also, would it be a bad idea to mod them on clamps and use it for my tank heater?

 

I glue egg crates to magnets to make frag racks....I think its a good idea