# How much air does a sponge filter need?



## Tejay (Jan 22, 2013)

hi All,

I have been looking around the web for an answer, there are a number of threads but none answer the question!
If I have a sponge filter rated at 130g, how much air do I need to pump into the filter to obtain this filtration?

Thanks

Tejay


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## triscuit (May 6, 2005)

Good question!

I don't know that I have the time to work through the math of it (yes, fluid hydraulics are fun!) but basically, each air pump has a volume through time rating- which is derived from it's pressure rating, sort of. The actual amount of movement will depend on the depth of the filter, its porosity and the temperature of the system... so there's quite a bit of variability outside of the air pump or filter capacity. In the case of rating the sponges, that's mostly about the amount of media available for filtration. I think those ratings are for convenience, and don't have any basis in actual practice. For example, a 130 gallon tank would typically have around 800 gallons per hour of filtration. Putting that through a single sponge filter doesn't make any sense... and would probably limit the ability of your biofilter to function appropriately.

I estimate a sponge's "capacity" by how much air I can supply without either moving the filter (they'll bounce around if given too much) or splashing outside of the tank (which is mostly irrelevant to the sponge I'm using). So, to provide sufficient filtration for a 130g aquarium with a single sponge won't be a factor so much of the size of your sponge filter or the amount of air supplied, but rather the hydraulics of what happens when forcing air through water.

So, the long answer to your question is that there isn't an answer that works across all systems. In general, though... to run a large tank solely on sponge filters can be done. though for a 130 gallon tank, I'd recommend 4 sponges spread out across the length of the tank, and water changes at least twice a week depending on stocking levels. The pump needed to power four sponges doesn't have to be very big... here's an example of a pump that could easily run enough air through multiple sponges for a big tank: http://www.drsfostersmith.com/product/p ... catid=3676


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## zimmy (Aug 13, 2010)

Thanks for the detailed response, triscuit! I was watching this thread to see what answers came up.

The link you referenced shows two pumps. Is it the 150 or 300 model you're referring to?


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