Middle

Works good, I have one in each side of my 15g planted shrimp aquarium. Water is clear shrimp look happy. It has it's own built in diffuser not air stone. Doesn't cause a bunch small or large bubbles making micro water droplets sprinkle out. Causing those little spots in top like others do when they kind of make that misty zone. Easy rinse amd squish to clean. Plug the hose on top good to go easy. Use a valve to control air output.

The small size (up to 10 gallons) is perfect for a 5.5 gallon betta tank. It's quite small so it doesn't take up too much room. It'd be easy to hide in a planted tank or with some driftwood. The base is heavy and it stays at the bottom after the sponge fills with water. I paired it with the Nicrew Air Pump and it's working great.

Works well with the micro hygger air pump. It’s doing a great job keeping a 5.6 gal tank clear and clean.

Works fine. A bit on the light side though, and needs persuasion to stay down.

i have two of these, one in each of my bettas 7 gal long tanks. i love that they fit into the corner. they are short enough to work in my shallow tanks. i have a dial on my air pumps so i use that to control the flow but i also used the simple plastic dial you can use on your airline tubing before i upgraded my air pumps, both methods work great at controlling the output on these. really don’t have any complaints. the price is great and i’ll definitely purchase another of these if set up any more betta tanks

This sponge filter is PERFECT for smaller tanks!! I have had it in a 3 gallon betta tank, and now have one in his upgraded 6 gallon. Since it's a short and stout sponge, it's easy to hide with plants and hardscape! Works great at keeping the tank clear and clean, and doesn't make much noise on top of that. Would 100% get again.

Very nice set up but the sponge is too coarse for my betta. I like the set up thigh, so I’ll be buying a large, round, super soft refill sponge to put on it.

I looked at measurements prior to purchase but this is much larger than what I had expected. Since it’s 1/4 cylinder and fits in corner it only works on the one side. 40 Gph will work for a 4 gallon tank and it is way too big to fit. The only reason I purchased it was to add additional oxygen to my tank temporarily while fighting a hair algae issue but an air stone won’t work with it!! So that was useless. Also there is no place for adding other filter medium. A small round one would work as well and be much less obtrusive.

This filter is so good. works all sorts of ways. I have mine hooked to an FX6 canister filter for my shrimp. Great buy.