How Do I How do I make DIY sponge filter

matt6765

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Hi in the near future I am getting a 72 gallon tank and I am planning to get/breed pearl gouramis in my old 26 gallon tank. So my question is how do I make a sponge filter for the fry tank.

Thanks,
 
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Red1313

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Depends how fancy you want the sponge filter to be.
I use an AquaClear sponge (either AC 20 or better, AC 30) slice a hole in the middle, wedge an air stone in and then you just attach it to the airline tubing and tada you're done. Usually I weigh the sponges down with some stones to keep them on the bottom but I hear that some other's don't.
To make this sponge filter design more efficient adding a piece of uplift tubing to the hole and then placing the air stone in there will help the water draw.

EDIT: LOL Massive double ninja
 
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matt6765

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How exactly does it filter water and where does it come back into the tank?
 
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Red1313

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Basically as the air forces the water up it draws new water into the sponge to replace it. The more current up and out the more water in. However the draw of a sponge filter isn't quite as effective as the draw of say a hob (which is why it's good for fry) but since water like things like ammonia to be the same concentration everywhere so ammonia toxins etc. are still taken care of fairly effectively but solids arn't so much.... and while they're center in and around the sponge to a degree they're not moved so much....

EDIT: 2nd attachment is just an example of a sponge filter I used while QTing my WCMM

Edit #2: Modified Sponge filter diagram
 

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bass master

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heres a diy sponge filter I will use on occasion, its made from some sort of small plastic cup, shredded scrubbing sponges (the kind you use for scrubbing algae off your tank), and a small amount of gravel from an established tank. Cut off the rim from the cup to get it to the desired length, cut up the sponge/rag and fill most of the cup, add a length of tubing into the middle of the cup and get it as deep into the shredded sponge as you can, then cover the top with gravel from an established aquarium. I also will add a bit of filter media from my main tank's filter to make sure I have a good bit of bacteria already in the tank. Really the tube is a pretty necessary part of the sponge filter because it is what actually draws current, without a tube the bubbles mostly scatter and cannot create an efficient current, IMO the longer the tube the better the filter will work
 

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Lucy

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The airline gets put down into the tube?
I don't know why but a simple DIY sponge filter makes me feel dumb. lol
 

bass master

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yep, airstone on the end of an airline, forced down the tube, forgot to say that. The airbubbles coming up the tube cause the column of water within the tube to be less dense then the water surrounding the sponge so the overall pressure within the tube is decreased, the excess pressure outside the sponge forces water through the sponge into the tube, where the new water is aerated and made less dense so on and so forth so a constant flow of water comes out the top of the tube, and you thought a $10 filter would be simple
 

Red1313

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My sponge filters have worked well without a tube. However I've also used them mostly on lightly stocked, small tanks with weekly water changes, so have never had to really test them.

Lol you're welcome lucy Basically if I were to add a tube to the filter I pictured above the air line tubing and air stone would simply be inside it. With tubing you also don't need to have the stone in the media itself since as long as the bubbles are forced up the tube water will be drawn in.

As to the length of the tube I don't know. I have a number of air driven box filters as well and none of them have a tube/chimney type structure more then a few inches long and are rated for 10-20 gallon tanks. I've used them in big tanks (mostly to keep cycled) and I've never noticed the air bubbles spread out. They always run straight up regardless of distance. I do suspect that smaller bubbles will work better then the larger once which I sometimes get with my particularly cheap air stones
 

bass master

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well without a tube the bubbles cant really suck much water through the sponge, but it will increase the amount of water flowing over the sponge so it can still serve as an effective biological filter. Air driven box filters I believe work also by using bubbles to decrease the overall density of the water within the filter, but instead of using the change in density to suck water through, it causes the water level within the filter to rise and then spill over into the tank, so theres not really a need for a tube, Im not sure about this though, Ive never actually owned one of those air driven box filters, this is just my assumption of how they work. Also an airstone will definitely help even with tubing because it allows for more air to remain in the tube so the difference in density within the tube is larger so more water can be moved.
 

Red1313

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well without a tube the bubbles cant really suck much water through the sponge, but it will increase the amount of water flowing over the sponge so it can still serve as an effective biological filter. Air driven box filters I believe work also by using bubbles to decrease the overall density of the water within the filter, but instead of using the change in density to suck water through, it causes the water level within the filter to rise and then spill over into the tank, so theres not really a need for a tube, Im not sure about this though, Ive never actually owned one of those air driven box filters, this is just my assumption of how they work. Also an airstone will definitely help even with tubing because it allows for more air to remain in the tube so the difference in density within the tube is larger so more water can be moved.
I think you're confusing density and flow.
What happens is air is pumped into the aquarium via the air stone. Air bubbles require a certain about of volume and to have that volume they need to displace an equal volume of water (similar to putting a finger in a full glass of water or working in you're tank one you've filled it up all the way). In the tubing the displaced water has no where to go but up the tubing with the air bubbles. With the water displaced and the air that displaced it moving up the tubing water is drawn in through the sponge to replace it. There isn't so much a change in density as simple displacement.

The same thing would occur if you simply wedged the end of the airline into the sponge (or placed it in the tubing). The action and reaction of the sponge filter and the UGF filter works the same way. Water it drawn through "media" to replace water that has been forced up.

Here's a corner filter
798.jpg

It works on the same principle but is a bit more well designed to take advantage of water's tendecy to flow.
The air stone here is located below where the media would be. Water it drawn through the top of the box. Down through the media to the bottom of the container. Here the airstone is at the base of a chimney which forces the water back up.

Water likes to follow water (think of a bunch of molicules holding hands in a big chain). As soon as the front of the chain starts to move (pushed by air) the rest of it follows like lemmings off a cliff. lol
 

bass master

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if it was only displacement forcing flow, you would initially get a push of water out, but once a certain volume of air is maintained in the tube, no more flow would come from displacement, the overall density of the water/air mixture within the column is less dense then the full water outside of the column, notice that the corner filter does have a lift tube within it. Technically a bunch of bubbles moving up a tube would move a small amount of water out of the tube but the more important force is the water pressure outside of the tube pushing its way into the tube which forces the bubbles upward, both are technically correct ways of thinking of it but really comparing the pressure differences between the pure water and the less dense air/water mix which will exert less pressure is a more tangible way to observe the forces IMO

edit: forgot to finish the last sentence....
 
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Red1313

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oh i'm not getting into forces... I did my time in first year physics in university and I'm not going back lol.
Let's agree to disagree and both be right Regadless of the actual forces and modes involved water moves from the main body of the tank, through the sponge, and out with the bubbles
We know this is how it works, why it works that way doesn't matter quite so much.
 

bass master

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haha Im currently stuck "doing my time"

true, as long as it works why worry about it, I just usually prefer to use lift tubes
 

Red1313

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haha was that what we were really arguing? lol

Lift tubes increase effectiveness. I, don't own any and make alot of sponge filters, therefore I don't use them
If you can do, if you don't have not going to stop the filter from working

we good now bass?


P.S.
Does this count as a highjack? lol
 

bass master

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haha well it is technically adressing the question? well let the mods decide

The part Im mainly debating is whether or not any water will be pulled through the sponge at all without a lift tube. But whatever works, we good
 

Red1313

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lol
I'll throw my camera on the charger and will set up an example for you Remind me tomorrow lol.
I know/suspect it works since you can squeeze a lot of nasty stuff out of the sponge filter.
 
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