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SPONGE FILTERS: Why and How

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#1 ·
WHAT IS A SPONGE FILTER?

Sponge filters are a staple among aquarium keeps that need a low flow way to filter tanks with delicate residents. Sponge filters are the best alternative for not only betta keepers, but also for new born fry and shrimp. They help provide stable water conditions without a strong intake which can damage delicate fins, or even suck small new born fry into a filtering system that would kill them. They are economical due to the fact they can be cleaned and reused instead of having to replace filter media. They come in a variety of sizes and can be purchased for next to nothing. About the only down side (in some cases) to using them is they are driven by air pumps which, depending on the brand and surface they sit on, can be louder than a HOB (hang on back) filter. Also they take up room inside the tank and thus are more visible than a HOB.

THE FILTER AND ITS FUNCTION
Sponge filters can come in an almost infinite variety of shapes and sizes, commercially produced or home made. Its main use is not to remove waste from the water (although it does do that) but is to provide a place for beneficial bacteria to grow. The larger the volume of water, the bigger the sponge needs to be to provide enough surface area for more bacteria. Some filters will have odd shapes or shallow channels. This is to maximize the amount of surface area for bacteria to grow.

HOW DOES IT WORK?
A sponge filter will consist of three basic parts; 1) a sponge 2) a tube rising up from the middle 3) an air line supplied by an outside air pump.
The airline is inserted in the tube. As air bubbles rise, they push out water, creating a void. At the bottom of the tube are holes under the sponge which allow water to enter to fill the void. Once beneficial bacteria have colonized the sponge, the water flowing into the sponge is then cleaned. Pretty simple huh?

MAINTENANCE
Depending on the size of the tank and its bio-load (i.e. how many fish), which in this case we are usually talking about one betta, you will need to clean the filter about once a month. To do this, first you want to get a container and put some tank water in it. This is usually best done during water changes. (NEVER use tap or new water as this will kill your marvelous bacteria colony you have waited so patiently to grow.) Remove the air line and tubing from the sponge. Place the sponge in the container of tank water and gently squeeze a few times. Replace the tube and air line and reset into tank. (Yes it’s that easy)
Q; How long will it last?
A; Depending on the material it should last for several years
Q; How often should I replace the sponge?
A; Not until the sponge starts falling apart when you squeeze it out! If you replace the sponge you will have to wait for a whole new bacteria colony to grow in the new one.

DIY SPONGE FILTER
Even though sponge filters are inexpensive, some of us just can’t resist the chance to say we made our own equipment. Sponge filters are the easiest thing you will ever make for an aquarium. (I designed and made my 35 gallon sump, so I know of which I speak)
Materials needed;
Sponge (make sure it is NOT an antibacterial sponge. Kinda defeats our purpose)
I use a car wash sponge from the dollar store shaped like a figure 8. They are stiff
enough to cut easy but soft when wet to allow water flow.
A plastic or pvc tube 1 inch diameter or less
Air tubing and air pump.
An inline valve or gang valve
A weight of some inert material such as slate to make a weight for the bottom (in small tanks, say 2.5 gallon, some people will put some gravel from the substrate to hold it down instead of weighting it)

First cut the filter. Depending on the size of tank is how big to cut it. Examples would be; for a 2.5 gal. you can cut one 2.5” in diameter X 3” high. In a 10 gal. you can do 3.5” diameter X 6” high. These are only starting reference points.
Next, cut the tube so that you have no less than 3” from tip to water surface.
Now put your cut sponge next to the tube and mark where, with the tube fully inserted, the filter sponge will come up to. Drill hole all the way through both sides, alternating sides as you go up to your mark.
CAREFULLY drill a hole in the center of the sponge slightly smaller than the tube.
If you are using a weight, affix the end of the tube with the holes you drilled to the weight. I use aquarium silicone for this. Let dry.
Now slide your sponge over the tube and push to the bottom. Make sure all the holes you drilled are covered.
Place the filter in your tank and squeeze so all the air goes out. Let rest on bottom.
Cut a place in air line to insert the valve.
Insert the airline all the way down the tube. Turn on air supply.
Adjust air flow so you have a steady flow of bubbles but soft enough so that the surface is not disturbed too much.

Be it factory made or DIY, you can now enjoy a cycled tank that will give your betta water quality he deserves no matter what size tank he is in, and cut down on his stress and yours with fewer large water changes.
 

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#7 ·
+1 to sticky vote

When I first started I didn't know jack about the options of equipment fish keepers have, and this is really one of the most underrated pieces of equipment even though they are very useful and less likely to break (less parts). Not to mention they probably aerate water more than a regular hob, internal, or canister filter.
 
#13 ·
Good job, Waterdog.

Two things to keep in mind when considering sponge filters:

As the bubbles pop at the water surface a gas exchange takes place which adds oxygen to the water. This is important for the health of the nitrifying bacteria and stock. Betta and Gourami don't care about this.

However, this gas exchange also drives out CO2. This tends to raise the pH level--- more or less depending on water hardness. If your water is hard and your pH is already high, this is something to consider.

Sponge filters are not calculated to enhance the beauty of your aquarium.

And two tips:

Wrap the often-noisy airpump in a towel, then hang it on the wall. This is as quiet as I could get mine.

If your pump is below the surface level of your tank, a one-way check valve will prevent back-siphoning if your power goes out.
 
#14 ·
I don't know, my air pump is perfectly quiet. It makes less noise than my laptop cooling fan while being perched on top of my betta tank (the air tube is stretched across my desk to the other tank).
Interesting point you made about the gas exchange Hallyx!! I know the disruption at the surface of the water caused my old VT to nip his fins bc he couldn't bubbles.
 
#15 ·
Thank you all for your comments and sticky votes!!!! :-D


Interesting point you made about the gas exchange Hallyx!! I know the disruption at the surface of the water caused my old VT to nip his fins bc he couldn't bubbles.
I have sponge filters in 3 betta tanks, a 2.5, a 5, and 2 in my 10 gallon and I have had no problems with either my fish or plant growth. As long as plants get the right light and regular water changes to replinish minerals in the water, they usually do fine. My 75 turns over water at the rate of 10 times per hour and it's like a jungle in there that I have to constantly trim back.

This is a picture of one of the two homemade sponge filters in my 10 gallon. I put two as I plan on dividing the tank soon.
 

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#17 ·
I know most breeder tanks do not use filtration of any sorts when the male betta is making its bubblenest but does anyone here actually use these in their breeding tanks? It's perfect for not sucking up the eggs nor fry. But do you find that the bubbles it creates is too turbulent for the bubblenest that the male bettas need?
 
#20 · (Edited)
Thank you all for the compliments and sticky votes!!!!!!!!!!




I am not a breeder and have no intentions of being one for awhile. I'm sure someone here that does breed can answer better than I can. I would think you could just shut off the air supply during spawning, then reopen after the hatch, but that is just a guess. :roll:
 
#21 ·
Putting a a piece of open cell filter sponge at the surface to catch the bubbles cuts down on surface turbulence.

Using an airstone on the bottom of your airfeed tube creates smaller bubbles and more of them. This cuts turbulence and is also more efficient,
 
#23 ·
Fantastic little gem of information! I do hope they they make this a sticky as this is has awesome information, plus the images on the original post gives an idea as to what to look for for filters. One website I was peeking through I wasn't sure what kind of sponge filter to get and almost just totally ignored them altogether. Good thing I haven't bought one yet!
 
#25 ·
Thinking about doing a DIY for my 2 gal tank, doing 2-50% and 1-100% water changes a week, what should I cut down to if I have a sponge filter or should I keep the water changes the same and just clean the sponge once a month?
 
#28 ·
We did a complete change from HOB to sponge filters last year on all tanks less than 10g. It was getting ridiculous the flow issues and breakdowns from the small HOBs. On larger tanks its good to have one of each in the tank as they can back each other up. The older the sponge the better and using the big tank to season up new sponge filters work well IME. Also a nice little trick is to take a pill bottle, fill it with media like Seachem Matrix, poke a couple holes in it and find a spot in the tank for it like inside a decoration or even attaching java moss to the bottle. It becomes an ammonia buster and can help keep a cycle stable.
 
#30 ·
I agree that this should be a sticky! Wonderful thread!
:)

A quick question though. I ordered a few sponge filters online (they were a couple of bucks each, less than the sponges at the cheapo store, haha!) and ordered two different sizes because I wasn't sure which would be best (the measurements were vague, it was eBay after all). Now they've arrived, one kind is teeny tiny, the other is massive in comparison to my 3.9gal tanks! Which of these would you recommend for a tank of that size (which will decrease in capacity slightly with the addition of gravel and more plants/hardscape)?

Small: 2.25" x 2"
Medium: 3.5" x 4.5"

That's not including the weighted bases and tube, just the sponge measurements. If I were to use the larger one, I'd have to saw some of the tube off, and sand it down smooth for it to fit under the water surface...

I wouldn't want to not have a large enough unit in the tank, it'd defeat the purpose of having one in the first place, but wow, is the "medium" big for where it'd be going! Heh.
 
#33 ·
I agree that this should be a sticky! Wonderful thread!
:)

A quick question though. I ordered a few sponge filters online (they were a couple of bucks each, less than the sponges at the cheapo store, haha!) and ordered two different sizes because I wasn't sure which would be best (the measurements were vague, it was eBay after all). Now they've arrived, one kind is teeny tiny, the other is massive in comparison to my 3.9gal tanks! Which of these would you recommend for a tank of that size (which will decrease in capacity slightly with the addition of gravel and more plants/hardscape)?

Small: 2.25" x 2"
Medium: 3.5" x 4.5"

That's not including the weighted bases and tube, just the sponge measurements. If I were to use the larger one, I'd have to saw some of the tube off, and sand it down smooth for it to fit under the water surface...

I wouldn't want to not have a large enough unit in the tank, it'd defeat the purpose of having one in the first place, but wow, is the "medium" big for where it'd be going! Heh.
The smaller one would be fine for the tank your putting it in as long as the only resident of the tank is 1 betta.
An example of how this works is simple. The BB colony is supported by how much ammonia is in the water. The more fish creates a larger 'bio-load' which needs more BB to handle it. On the other hand, if you have 1 fish, your bio-load is smaller and requires less BB.
If you had a tank with say 10 fish and you took 9 out, some of your BB would actually die off as there is not enough ammonia to feed it all. You can't have more BB than ammonia to support it. Natures checks and balances system is pretty effecient!
 
#31 ·
While this thread is going I wanted to throw you guys a question...

So, I didn't do full research like an idiot when I was filter hunting. I got my filter alright and it's exactly the one I wanted but... for some reason I thought it would come fully equipped. Uh. No. Silly me. What air pump or air stone system thingie would you guys recommend for me to use with this? It's a Hydro I. I have utterly no experience when it comes to pumps and the like. I only have better ideas with power filters over these weird thingamajigs.
 
#34 ·
While this thread is going I wanted to throw you guys a question...

So, I didn't do full research like an idiot when I was filter hunting. I got my filter alright and it's exactly the one I wanted but... for some reason I thought it would come fully equipped. Uh. No. Silly me. What air pump or air stone system thingie would you guys recommend for me to use with this? It's a Hydro I. I have utterly no experience when it comes to pumps and the like. I only have better ideas with power filters over these weird thingamajigs.
I'll defer to Hallyx on this one as I really have yet to find an air pump that I am crazy about. So far, to me, one is pretty much the same as the next.
I do agree silicone tubing is ALOT better than the cheaper plastic tubing. For the pennies difference it's definately worth it!
 
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