I went to the dollar store and bought a few shower caddies. then took a wire coat hanger to cut/bent to hang the caddies from the edge of the tank. I tried suction cups for a while but they kept losing suction and would sink into the tank, with that said I don't recommend suction cups. I lined the inside of the caddie with mess laundry bags. place substrate, plants and done.
If you don't want to go the DIY route...
you can purchase kits as well at ripariumsupply.com
+1, Stick to a suction cup alternative, such as coat wire or something that hangs onto tank's edge, Im considering using black hair net that's clipped to tank edges.
I just don't want to have floating suction planters upon returning from a vacation.