Two Little Fishies BettaMag is an even smaller window-cleaning apparatus than NanoMag, designed for use on Betta and Goldfish bowls or Pico aquariums. In small bowls or Pico aquariums the NanoMag is so strong it actually moves the whole tank when you try to clean the windows! BettaMag solves that problem by being sized just right. It’s ideal for glass with a thickness of 1/8 to 1/4 inch. Patented design by Julian Sprung.