# Is a Sponge Pre-Filter as good as a Sponge Filter?



## zfarsh (Apr 7, 2011)

Ok, so another newbster question.

So i have 2 filters in my 10g tank, and both have sponge pre-filters, ie, i cut a rectangular sponge and made an X in it, and fitted the inlet of the filters in it. The purpose is that little shrimpies dont get sucked in. However, apparently, dedicated sponge filters with an air line are necessary for shrimps, specially for the CRS kind. So my question is, is my sponge pre-filters just as good for the CRS, or do i absolutely need dedicated sponge filters with the air line? Will the necessary bacteria or biofilm or whatever it is these sponge filters have also be created on the sponge pre-fitlers i have on my HOB and soon cannister? I used to have one, but my new aquascaping and space available doesnt leave room for it, unless i ditch one my filters, which i would think would be less good .


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## getochkn (Jul 10, 2011)

The benefit of a sponge filter via air is that the bubbles from the sponge filter break the surface tension of the water, promoting a high O2 exchange and bring O2 into the water. Most people think the bubbles are bringing oxygen into the water, but they're not, they're breaking the surface with thousands of bubbles per minute, bring O2 into the water.

Shrimp like lots of O2. Being bottom dwellers, less O2 is at the bottom of the tank than the top. Most fish are top to mid dwellers or roam around the tank and get more O2 into them. Shrimp are usually at the bottom, the least O2 rich area of the tank, so getting more and more O2 into the water helps and benefits them. Many bacteria are anaerobic, which means they do best in a low O2 water, so the more O2, the less chance of them forming.

You can get the same effect by having a spray bar above the water splashing down, HOB filter causing some splashing and surface agitation, air stone, air-powered under-gravel or sponge filter, etc but since sponge filters provide a spot for them to graze and aid in adding O2 to the water, it's a win-win situation. 

You can't over do it either, the O2 in the water, at MOST, will only saturate to the levels in the air. Part of the reason if you look at shrimp breeding tank, not just keeping or pretty planted tanks, but big breeding tanks, the water is always a few inches low and the have a huge spray or drip bar with the water from the filter coming a few inches above the water, it's to help get more O2 into the water.


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