Penn Plax 12-Pack Small World Filter Units and Replacement Cartridges for Small Tanks

This is one of the best filter systems I’ve ever found for delicate fish or smaller bettas. Be sure to try to buy the cartridges in bulk as they’re so much cheaper than individually. I have been using this brand for almost a year now and change them every 6 weeks to 2 months. I highly recommend them in that the flow is low and calm for my betta Tye

I have a breeder tank with guppies who would get sucked into the filter, if not for this. It is quiet and safe for them and other small fish. I used these for at least 30 years, but couldn't find them. I am so happy I could get them from you!

I've tried MANY. This is the best filtration for a small tank, Up to 3 gallons. I'd recommend dual for more than 3 gallons. They're easily visible and easy to change.

It does what it's supposed to do and it does a great job at filtering the water with very little disturbance...but it does not fit well in a round bowl like the picture suggests.

If you're buying the replacement filters odds are you already own the actual filter. This deal is way better than what my local fish store offers and this filter has been perfect for my little 4 gallon jar planted tank. Hell of a deal, legit product, works perfectly.

This product I would use every month, cause it's the best item I found for a fish tank !!!

My local pet stores sell the unit but not the replacement filters. I raise pinhead tadpoles until they grow into frogs in an effort to replenish our dwindling amphibian population due to an illegal spraying situation years back. It appears to be finally taking hold as I rescue these tads from neighbors pool covers in the spring. This is the only filter I have been able to find that does not allow the tiny tadpoles to be able to get sucked in or stuck. Great product!

Does a great job! Just wish you could extend the life of it by taking the sponge out and cleaning it. I have mine in 3 betta fish bowls and it's great!

Simple to replace and efficient.