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?
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)
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.
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.
Yes, please sticky! Too many people get HOB filters for their bettas and end up with shredded fins, or even worse, dead fish. This seems to happen over and over again and I think we should all be nudging people to get sponge filters. They are superior in safety.