Aqua Clear AquaClear Foam Filter Inserts, 3 Pack – Replacement Mechanical and Biological Filter Media for 70 Gallon Tanks

This is the same sponge that you get with your filter, it will work the same way. It's cheaper than most local pet stores will have them available for (though at my LFS the full filter was cheaper to buy in store but the media (sponges, carbon, etc.) were much cheaper here on amazon. I love the filter and these sponges, the only thing I'd say is that the recommended replacement time is clearly designed to sell more of these. You can easily make one of these sponges last over a year just by taking the sponge out of the filter, squeezing the sponge out, and rinsing it (I recommend rinsing in old aquarium water after you've done a water change, not while it's in the tank so you don't add chlorine or chloramine from the tap). An added advantage of continuing to use the same sponge for a long time is that it will keep your beneficial bacteria alive and well in the sponge effectively letting these function as both biological and mechanical (but NOT chemical if you're into that) filtration!

This is a great filter! You can see on the picture that is does a great job at keeping gunk out of the water. It is easy to use and I have been washing mine and reusing it a couple of times before throwing it away.

It’s a foam filter insert. Good value

I like using these opposed to buying those flat blue filters with carbon infused. My fish hate those things anyway and never feel well. I have bought these twice and they work great! I can customize the fit by just cutting the individual sponges for my hang on the back filter and combine with biomax etc. Needless to say, my large pleco is very happy and healthier since switching to this product.

It can be better if a little bigger

Use these with Emperor 400 filters. Unfortunately they are hard to find now or discontinued 😭

Keeps my fish tank clean

Good, firm, very open cell foam, slice to size for various applications.