Sponge filter and bacteria culture

[Don Trinko]

I have a 75g tank with 4 4" to 5" discus in it. I have a 250 gph HOT filter with the standard media in it and a sponge that is rated for a 40g tank. The idea of the sponge was that if I ever have to completely change the HOT I will have a bacteria culture in the sponge.
Will there be sufficient bacteria in the sponge to take care of the amonia and nitrites? Thanks; Don T.

[Tropical Haven]

If your main filter goes out and you need to rely on your sponge filter one isn't going to be enough for that size tank. I would place another sponge filter in it, because thats a lot of bioload on one sponge. Rule of thumb that I use for myself is anything over 30 gals gets 2 sponge filters in it or more depending on the size of the tank. On my 125 gal tank I have 4 sponge filters and 2 penguin 350 filters hanging on the back.

[Don Trinko]

I'm thinking abought adding another 250 gph HOT with the micron filter. I have one that I use to "polish" the water in various tanks. I presume the micron cartridge would develop bacteria also. Don T.

[Apistomaster]

I'm thinking abought adding another 250 gph HOT with the micron filter. I have one that I use to "polish" the water in various tanks. I presume the micron cartridge would develop bacteria also. Don T.

Hi Don,
The small additional surface of a micron filter will not make any contribution to maintaining nitrifying baacteria colonies. Just add a nice big sponge filter. It will add the reserve capacity you are seeking. Just a couple of big sponge filters are the only filters you need when it come right down to it.

[caldwell]

For my 75g growout/holding/display tank I use double stacked hydro-V sponges with a powerhead. I could probably triple stack if I wanted to. Works great for me!