Best bio filter media for 10 gal tank?


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Aug 13, 2017
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My 10 gallon aquarium came with a penn-plax cascade 300 internal filter. The filter includes a sponge and activated carbon cartridge. After learning that activated carbon is pretty much useless except for removing medications and chemicals, which I don't need (and also removes tannins, which I do not want) I want to replace it with something else. Any ideas of what kind of media I should use? I was thinking about crushed lava rock, or porous ceramic.

Also, how would I go about switching the media in a cycled tank? I know the filter media contains all the nitrifying bacteria needed for the nitrogen cycle, so how should i replace the media without disrupting the cycle too much? (The sponge is staying)

future inhabitants of my (newly) cycled tank will be 1 giant Betta and a few nerite snails
Roughly what % of the total media does the sponge make up?

What PPM of ammonia did you cycle with?
I think about 50%. The sponge takes up half of the filter.

I tried to stay around 2 ppm
As you've no fish in the tank, you're safe to replace the whole cartridge. In a stocked tank, you normally don't change more than a quarter of the total media at once. You might need to cycle for a bit longer before you can stock, of course.

As you're not intending to stock with a lot of messy fish, I'd recommend adding another sponge; just aim for a coarse one, rather than a fine one. Sponge is a perfectly good bio media, as long as it's not going to get clogged too quickly.

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