# Sponge Filters



## paavn (Jan 15, 2009)

if i got a decent sized biosponge and inserted an airstone into it, connected it to an air pump and put it in the tank, would that be sufficient to make a sponge filter?

its for a 5 gallon tank that i plan on only have shrimp in with some moss and riccia


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## aspects (Feb 1, 2009)

I would go without the airatone diffuer on the line and put the line straight in. However a DIY sponge filter is pretty easy to make with a sponge, a piece of pvc, a small tile or piece of slate (whatever is available to you), and some airline tubing.


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## justintrask (Jun 29, 2008)

i have used sponge filters both with and without airstones, and i recommend using the airstone just because it causes more bubbles, which causes more frequent suction, rather than big bursts of suction through the sponge


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## aspects (Feb 1, 2009)

imo the stone diffuses the air coming out, and you dont get nearly as much "suction" as you do with the larger bubbles coming directly from the line, thus making the sponge portion less effective. if all youre looking to do is aerate the water, go with an airstone and no sponge. but if youre going for the bio/mech filtration of a sponge filter, youre best off with a straight airline.


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## paavn (Jan 15, 2009)

I guess I could try both of them and find out which one I like better lol


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## emc7 (Jul 23, 2005)

I kind just stopped using airstones in my hydrosponge filters and they are fine w/o. You will wand a small rigid tube to attach the airline to and a larger rigid tube to make a "chimney" for a the water coming out of the filter to rise. It can be PVC or clear PS. You can buy clear rigid tubing onilne and at some LFSs. I've never DIYed one, they are so cheap to buy, you'd need to be making a bunch or already have materials to come out ahead.


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## redpaulhus (Jan 18, 2005)

I've got something someplace that looks at the flow dynamics of large bubbles, small bubbles and very very fine bubbles in a riser stem from an applied physics point of view (hydrodynamics etc) - I forget if it was in Moe "Systems and Inverts", Calfo "Book of Coral Propagation", or one of my textbooks from way back in college.
I'll grab it and try to get some exact quotes.

Technically - I think a greater volume of small fine bubbles create a more constant area of low pressure and lower specific gravity (density), causing a greater total flow, as opposed to larger more infrequent bubbles. 

However, on the scale we're looking at, and the rates we're talking about, the difference between having an airstone or not is pretty insignifigant. (ie a 1 - 10 % flow rate difference in a four-inch long lift tube of 1" diameter really doesn't mean much).

Like emc7, I rarely make my own sponge filters.
By the time I pay for a decent sized sponge that I trust (ie no fungicides, mildicides, fire retardants etc) and the lift tube and the base (4" slate squares work well but are hard to find) I find it would have been cheaper and faster to buy a hydrosponge, Dirt Magnet (for small tanks), or Angelsplus brand sponge (usually less than $5 for a small filter, $5 - $10 for a large).


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## emc7 (Jul 23, 2005)

I think the argument for airstones is that smaller bubbles are quieter. The argument against is that they will eventually clog.


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## smark (Dec 2, 2008)

Air stone is quieter. We have to have one in our bed room aquarium. The fish start to go crazy at first when the air stone is removed from the extra noise. I'm sure in a short amount of time they would settle down. It did seam like better flow without the air stone in the hydro sponge, but a little more noise.
I think Ill try without in the basement aquarium for a while and see how that goes. :fish::fish::fish:


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## TheOldSalt (Jan 28, 2005)

emc7 nailed it. Airstone versions do move a lot more water and make a lot less noise, but they do clog up and need replacing all the time.

The compromise I use is to use a hot needle to punch a bunch of small holes in the end of a piece of rigid tubing, itself sealed off on the end by heat. It transforms the tube end into a clog-free airstone which will fit into the small airtube inlet hole of most riser tubes.


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