# Calculating the capacity of sponge filters



## Fishy_Cichlid (Aug 4, 2011)

Hi all. I am currently cycling my 300 Ltr tank. The tank came with a powerhead connected to 4 strainers at the top (just below the alnico aquarium cover) where i put in my filter elements. As per specifications mentioned for the powerhead, it says it has a capacity of 1600 L/Hr Max capacity. I have installed 2 additional sponge filters connected to 2 airpumps. The specification on the airpump box says it is 3.5 Ltr/Min.

The primary purpose of the airpump, i believe, is to pump in air into the aquarium water & not filtration (Please correct me if I am wrong, since i am new to this hobby). But if it is connected to the sponge filters, I would like to know the filtration capacity of these sponge filters ? *Is it the same as the capacity of the airpumps i.e. 3.5 L/Min ???[/b]*


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## mccluggen (Jul 5, 2008)

The air pump is used to move water out of the tubes coming from the center of the sponge filters. Depending on how much air it is pushing, it will displace more water causing water to move through the sponge which actually does the filtering. The sponge is mostly just to provide a place for your bacteria to colonize.

However, with larger sponge filters you can skip the air pump all together and install powerheads on the lift tubes. These move a lot more water and make the filters more efficient.

As far as their filtration capacity that is hard to say. The sponges provide a lot of surface area, so the variable is how much water is moving through them. I don't have enough experience with sponge filters to comment 100%, and I am not familiar the main filter you are speaking f under your hood, but my gut says that you are probably okay with filtration with your current setup. You can do some things to optimize it, but may not have to.

Are you feeding the tank with an ammonia source to start the cycling process yet? Once you get things cycled the easiest way to find out if you have enough filtration is to add ammonia and then test your water after 24 hours to see if it is still there. Not much you can do to gauge your filtration capability until the tank is established.


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## Fishy_Cichlid (Aug 4, 2011)

Yeah, you are right. Should be fine. I am on the 14th day of the N2 cycle and my NO2 has already peaked, way beyond the 2.0mg/L mark. 
I was a little surprised by the specifications on the airpump. I believe capacity of an airpump should be NM3/Hr of air (or whatever gas) !!!! Was a lil taken aback how could an airpump have specifications in terms of Ltrs.
Anyways thanx for the advice.


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