Review on Aquapapa 4X Bio Sponge Filter: Ideal Betta Fry Aquarium Solution for Tanks up to 15 Gal by Kim Kawana

I use it as a secondary filter in a 29 gallon planting aquarium with 2 female bettas, some other small fish, snails and amano shrimp. I suspect it does the job, but there's no way to know for sure, and I don't plan on using it alone any time soon. I leave it on in case I ever need to fill up the quarantine tank, or I can run it on a backup battery in case the power goes out. Seems well made, hasn't fallen apart in over a month of use and I have 3 more if I want a deal this good. I'm deducting a star because I can't stand the sound of bubbles escaping from it and breaking the water's surface. Thank goodness the tank is down on the lower level so I don't have to hear it most of the time.