Homemade Sponge Filters

Cheaply made, highly efficient Sponge Filter

Material List:

• 8 inch length of 1/2 inch or 3/4 inch PVC pipe (Lowes, Homedepot) approx $2.00 for a 10 foot pipe
• 4 inch by 4 inch block of foam rubber (different sizes available from Lowes, Home Depot or Walmart etc) Very cheap.
• 8 inch length of rigid airline tubing (Available at Petsmart for about $2.00 for a 4 foot length)
• Marbles, slate or rocks to use as a weight for the filter
• Silicone for glueing the parts together

Notes On Construction:

These filters can be made in bulk quantities faster and cheaper. Be sure to get "open pore sponge", to be sure that's what you have you can try to blow thru the sponge, if you can, it's open pore = good, if you can't, it's closed pore = bad. Making the uplift tube: Cut the PVC pipe into 8 inch lengths. On the bottom of the uplift tube drill a few holes to allow the entrance of water into the pipe from the sides. You can either drill holes or use a hacksaw to cut slits, either way is fine.

Silicone the rigid airline tubing on to the inside of the uplift tube. An alternate way to accomplish this is to drill a slanted hole so that the rigid tube can be slightly bent and forced to the bottom of the uplift tube. Natural friction will hold fast the rigid airline tubing. Cut up the sponge into 4 inch cubes, larger or smaller, it's up to you.

Cut or drill a hole in the sponge to snugly accept the PVC uplift tube. One way to do this is to wet the sponge and freeze it to allow easier drilling. I find that just plunging a razor knife into the dry sponge works quite well. Be very careful.

The sponge is going to naturally float until it is well water logged, that's why the marbles or slate is used as a weight to help hold the sponge on the bottom of the tank. I prefer to silicone a piece of slate or tile to the bottom of the sponge filter. (I have found that hot glue will come undone under water, but your luck might be better, or I might have the wrong kind of hot glue)

Now hook your filter up to an airpump and it's ready to start filtering.

A quick way to populate the sponge filter with "good guy" bacteria is to run it a week or 2 in a tank with an established sponge filter. Or squeaze an established sponge filter in the water of the new tank so that the new filter will suck up the bacteria released from the established filter.

These filters are very efficient. One of these in a 10 gallon tank will supply all the filtration required to keep it clean and balanced. The costs of these filters if made in quantities of about 10 at a time will be under $2.00 each. Pretty good deal huh?

Questions And Comments

Q. The material list for the DIY sponge filter calls for a 4" block of foam rubber, but the instructions call for a sponge of the "open pore variety".....can u tell me exactly what i am looking for at Home Depot, Lowes, or Walmart..

A. Look for foam that has large pores. Also it is critical that it be open pore, to determine this you'll have to hold it to your mouth and try to breathe thru it. If you can breathe thru it then it is good. Try to do this without looking too weird.

Q. To keep the sponge from floating, are the marbles or weighted material just dropped down the center of the sponge?

A. You can do that, or you can silicone them to the bottom and make some "legs" for it. That would be beneficial for fry as it would keep the sponge filter off the bottom where it might trap fry. Larger rocks or slate would work also.

Q. Lastly......."rigid" airline tubing is just the normal air tubing...(clear or blue) thats sold at petsmart, walmart, etc??

A. Most petshops will carry rigid airline tubing. This is hard plastic tubing not the soft flexible tubing. It is usually sold in 3 or 4 foot lengths. You can use a knife to score it and then break it off in the right length to fit the sponge filters.