That's good one and I used 1 before until it's broke. It's really bulky and limited option how to put (mount) it in your tank, the foam clog really fast if you have heavy stock, best if you have a sump.My friend got this and put it on his 90g Tank and I couldn't believe the difference.
https://www.amazon.com/Green-Killing-Machine-Internal-Sterilizer/dp/B002ZVODP0