# Stupid question about air powered sponge filters



## mordalphus (Jun 23, 2010)

You should see water coming out of the uplift tube when it's above water. If you lift it far enough out of the water to expose the uplift tube, does water come out with the bubbles, or do the bubbles just stay in the tube.

They don't polish water like a canister filter though, they are purely biological. As long as water is moving through them, they're working.

If you want to polish water, you need to use a canister or HOB, or something you can put polishing media in.


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## captmicha (Jul 12, 2009)

I don't understand what you mean about whether water comes out with the bubbles? Water should be overflowing out of the tube when it's above the water line? Is that what you mean?

If you add a water pump with enough power, then it's not just biological anymore, right?


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## sceraxn (Jun 23, 2011)

I think what he meant is that when you lift the tube slighty out of the water then the water inside the tube should still rise out of it if the pump youre using is powerful enough. What youre really wanting is high velocity of water in sponge filters. You can do this easiest in two ways. Either get a larger pump or add an air stone to the sponge filter(if you arent already using one). You also want the longest section of up lift tube as possible for the sponge filter.


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## daFrimpster (Mar 7, 2005)

I disagree about high velocity in sponge filters. These are biological filters. The slower the water moves through the filter the more time it is exposed to the nitrifying bacteria in the sponge. Sponge filters are more efficient with slower water flow. Part of the attraction of sponge filters for breeders is that they don;t create a great deal fo current in fry tanks.


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## trixella (Jan 24, 2011)

I read a couple of days ago that you want to be sure that the air tubing reaches far down to the bottom of the intake tube inside the sponge in order for it to work properly. One of the fish stores here always has lots of dead and diseased fish in their tanks and I noticed that all the air tubes in their tanks only go about half way down the intake tube, they don't even reach down into the sponge portion at all.


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## roadmaster (Nov 5, 2009)

Have used Hydro sponge filter's for a few years now. 
Airstone should be inside the sponge and depending on the air pump, the force of bubbles rising in the tube, will provide some mechanical filtration but mostly biological.You will be surprised at the dirt,mulm,that is squeezed from these filter's with weekly cleaning.(squeezing)
The longer the hose from the pump to the sponge filter,,the less the force of bubbles will be rising in the tube. Shorten the distance and bubbles will increase.
I use luft air pumps which are plenty stong enough to run two Hydro V sponge filters in a 75 gallon tank. They are a bit pricey, but last much longer than my second choice, Whisper pump rated for 60 or 70 gal I believe.
It is the force of the bubbles rising in the tube that pulls dirt,mulm, into the sponge. Weaker pumps,or too long of hose,will decrease the force of bubbles rising and thus not much will be drawn to the sponge.
Hope this helps.


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## roadmaster (Nov 5, 2009)

trixella said:


> I read a couple of days ago that you want to be sure that the air tubing reaches far down to the bottom of the intake tube inside the sponge in order for it to work properly. One of the fish stores here always has lots of dead and diseased fish in their tanks and I noticed that all the air tubes in their tanks only go about half way down the intake tube, they don't even reach down into the sponge portion at all.


+one.


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## Sharkfood (May 2, 2010)

> The slower the water moves through the filter the more time it is exposed to the nitrifying bacteria in the sponge


This has little effect on the efficiency of a biological filter.

Faster moving water is in contact for less time, but is recycled back into the filter more quickly, resulting in an equal amount of amines being converted.


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## sampster5000 (Oct 30, 2010)

All we use at our fish shop are crappy little sponge filters and I can say that the tanks with slow moving water are always murky and need more frequent water changes. I recommend a good amount of flow unless you're keeping fish or inverts from slow moving water.


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## captmicha (Jul 12, 2009)

> I read a couple of days ago that you want to be sure that the air tubing reaches far down to the bottom of the intake tube inside the sponge in order for it to work properly. One of the fish stores here always has lots of dead and diseased fish in their tanks and I noticed that all the air tubes in their tanks only go about half way down the intake tube, they don't even reach down into the sponge portion at all.


I read just the opposite. That the air above the sponge provides the suction. If the air is at the same level as the sponge, what's to prevent it from diffusing out of the sponges?

The Luft Air Pump prices hurt my wallet.


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## [email protected] (Jul 17, 2008)

There are several scientific papers on line that discus lift tubes. They tend to cover lift tube several inches in diameter, but the principle is the same. Air bubbles lift water, they don't suction it. Ideal size for air bubbles is the diameter of the lift tube. 

That said, Hydor has been in business for a long time and they put the air line smack dab in the middle of the lift tube and sell bullseyes that make lots of small bubbles. 

{sigh}

My favorite is box filters, again. Marbles in the bottom for weight and floss or a sponge on top. You get the benefit of bio filtration, micro-organisms for fry if you leave the top off, and quickly replaceable media.


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## daFrimpster (Mar 7, 2005)

Sharkfood said:


> This has little effect on the efficiency of a biological filter.
> 
> Faster moving water is in contact for less time, but is recycled back into the filter more quickly, resulting in an equal amount of amines being converted.


I see what you are saying. I still not sure I agree but I see your point


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## jstehman (Dec 13, 2010)

I've used those sponges for years now, and they are "excellent" at bio-filtration. You put your airstone with a 1" piece of tubing connected to the bullseye, then your airline to your pump. Works every time.

I just cycled a 20gallon in 3 days with a size 3 that was in a 10 gallon for about a month. 

You're still gonna need to gravel-vac.
http://www.sponge-filter.com/


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## kcoscia (Jul 24, 2013)

is an air stone required for sponge filters to work?


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## Dragonfish88 (Jul 17, 2013)

kcoscia said:


> is an air stone required for sponge filters to work?


depending on the sponge filter you can put an airstone in it if you choose to. but it's generally not required


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## kcoscia (Jul 24, 2013)

what benefits would an air stone provide?


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## Dragonfish88 (Jul 17, 2013)

kcoscia said:


> what benefits would an air stone provide?


remember biological filtration is done through the movement of the bubbles. the more bubbles and smaller sizes for those bubbles means more "pulling force" since the the overall surface area on the smaller bubbles adds up.


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## kcoscia (Jul 24, 2013)

seems like it is worth the purchase since you can never have too much biological filtration!


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## GraphicGr8s (Apr 4, 2011)

captmicha said:


> I read just the opposite. That the air above the sponge provides the suction. If the air is at the same level as the sponge, what's to prevent it from diffusing out of the sponges?
> 
> The Luft Air Pump prices hurt my wallet.


The air bubble wants to go straight up. Path of least resistance. 

Using an airstone to get a fine mist of bubbles will move more water than large bubbles.

A sponge filter, although primarily biological also does mechanical filtration. 

Back when I was heavily into breeding fish all I used were the old round Lee's sponge filters and some box filters. Never had a problem with water clarity. 

The main advantage to a sponge filter in breeding tanks is the fry don't get sucked into an impeller. In some of the breeding tanks I use to use the Aquamaster HOBs. They were great and if fry did go up the siphon tube they were usually the best fed.


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## kcoscia (Jul 24, 2013)

I'm going to use it in a 5.5 gallon tank for a betta. Good biological, aeration and low current. It seems like the air stone is a good idea. What about check valves? Are they really needed?


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## Rocky5 (Jul 26, 2013)

kcoscia said:


> I'm going to use it in a 5.5 gallon tank for a betta. Good biological, aeration and low current. It seems like the air stone is a good idea. What about check valves? Are they really needed?


Yes there needed, even if you pump is above the water level, they just add an extra safty point.


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