DIY Filter Cartridges for HOB Filter

I installed and cycled my tank using the included cartridge, but I wanted to use my own media so that I don't need to keep buying filter cartridges, which can also harm my cycle, and so that I can transfer media to my Quarantine tank after sterilizing it between uses. How should I do this? I think I need filter floss, some sort of media for the bacteria, and possibly some other ingredients. Any advice would be appreciated!

What is your filter make and model number?

For my AquaClear 110 I cut poly batting (from craft store) to place on top of the sponge, and place ceramic rings on top of that.

Aqueon QuietFlow 30. I'm more interested in what type of media you used to house your bacteria. You mentioned a sponge, I've also heard of bioballs, carbon filter pads, and others. Would just a normal sponge do it?

Get a open cell foam sponge (not a normal dish sponge), I've heard you can also use plastic pot scrubbers. The foam you want is similar to that used in the smiley face scrubbers. You may be able to pick up replacement foam for various HOB filters and cut to fit your filter. The ceramic media I use is the Fluval cylindrical rings. A foam prefilter also helps to keep the internal media clean and provide more bacteria media.

There are several myths in this hobby concerning filters, cycling, etc. If the aquarium is established (a few months), you can change the filter media without any concern for recycling. There is more bacteria living in the substrate than in the filter. If you have live plants, you can do this from day 1 with no concerns. "Sterlizing" filter media will likely destroy any nitrifying bacteria anyway; it is easier to use live floating plants!

For DIY media I use coarse sponge, followed by a layer of filter floss and ceramic rings on top. You can just cut off the floss from your cartridges and add more media. I will say the floss isn't necessary but in your case it is since it has most of your BB on it and you will want to seed the new media that you won't need to replace (sponge and/or rings).

Hard to tell the exact water flow, but it looks like you could cut a piece of foam to fit where the cartridge is and place a cut piece of poly batting (or two) to hold in place in front of the foam. If you can, put a mesh bag with bio rings in front of that so the filtered water flows thru it. Not sure if you could modify the front section, or just remove and glue a few cross pieces cut from the old sponge holder to ensure the bio bag stays in place. Make sure that the media stays submerged. You may be able to place the empty cartridge in back of the foam to form a plenum so water will evenly flow thru the new media. Even if you cram the main body with foam and do nothing else, you will likely get better filtration and save money.

Buy a filter sponge for another brand of filter and use a pair of scissors to cut it to fit your filter. Sponges last for years and can be squeezed out in a bucket of tank water and the sponge gets re-used.