Mini Aquarium Filter Biochemical Sponge Fish Tank Oxygen Freshwater Pump Water Cleaner

I have this filter on a USB powered air pump on a 12" bowl (~3.5 gallons) and it works well, I wouldn't go any bigger than that with it. I rinsed everything in tap water and soaked in a mature aquarium before using to build up some bacteria on it to quick cycle the new planted tank. Only complaint is that the sponge is baaaaarely tall enough, it almost doesn't cover the top set of holes in the plastic inlet tube and there is a small gap between the sponge and the suction cup ring. This leaves the potential when installed to have water that passes through the tube without first going through the sponge thus not filtering. In the future I may try to find a larger sponge I can cut down to fit or see if I can cut out a bit of foam from the inside bottom of this sponge to get it up higher to compensate.Edit: now that I have had this running for a while, I discovered that the airline inlet tube on the filter is slightly larger than your standard clear PVC airline tubing, but if you plan to use it with the included or other Silicone airline tubing, it works just fine. The airstone inside is also kind of an oddball size so when it clogs you will have to boil/sterilize and reuse it. I have tried with other cheap blue airstones and a Ziss never clog airstone, but nothing else fits.Edit2: I realized the air stone was getting fairly clogged so I soaked it in a tiny cup hydrogen peroxide for an hour to clean it then rinsed it well in water, worked well to turn it white again and clear the pores. The flow through the sponge is there obviously because gunk comes out when you clean it, but the fine foam that the sponge is made out of and the short lift tube severely limit it. You can watch the lightest of materials, even specks of flake food, drift right past the sponge and they rarely collect on it.

I was really looking forward to trying out these little filters when I first saw them. I keep Bettas & these are just about perfect for smaller tanks. I don't like to advocate keeping them in really small tanks but if someone is going to. at least have a filter! This is basically a little sponge filter that just uses an air pump & some airline tubing (a short piece is included with the filter). I love sponge filters but sometimes the bubbles can be large & disturbing in a smaller tank & Bettas especially tend not to appreciate that. This one has a little airstone inside & with the suction cup it can be placed right at the surface to minimize the agitation even further. I would not use one of these in a tank bigger than about 2-3 gallons but in a 5 you could easily use 2. I sometimes utilize a 1-2 gallon hospital tank & these are perfect for that size. The pictures I posted show the parts all separate, all put together, in my hand to show size & one of them going in one of my larger tanks to cycle. All in all I'm very pleased with this little filter & am planning on getting more.

Great in betta hospital tank and second filter in 5 gal betta tank

Teeny tiny but fits in this 3.5 gallon

This is a great addition to my small aquariums. Even my betta is ok, it does not creat much water movement.

Very nice little filter. Gets the job done (in my 2.5 gal) and is very cute!

Small but perfect for 2.5 and 5 gallon tanks. I'm using it for a 10 gallon tank of red ramshorn snails. LOVE IT