A homemade filter for tiny tanks

written by: Matt Lichter

This is a small zeolite filter I've used in tiny, temporary tanks. Right now I'm using it in a 2 gallon tadpole tank, stocked with a few tiny tads. I wanted some type of filtration, but didn't have the time or energy to go through the cycling process before introducing the tads. I figured I would just use zeolite, since for the short term that seemed easiest to me. Since it was such a tiny tank, I was also looking for something cheap -i.e. DIY.

1. Find a small plastic container such as a film canister, prescription container, empty fish-food container, or any other small plastic container that isn't contaminated with detergents or other harmful substances (i.e. no shampoo bottles). Rinse well with tap water. (Film canisters may contain trace heavy metals, so add some tap water conditioner in the rinse, one that says "detoxifies heavy metals".)

2. Find about 3 to 6 inches of 1/2-inch tubing. This could be from the pet store or polyethylene tubing from the hardware store. Cut a notch the bottom end (see figure), or cut it at an angle. This ensures good water flow.

3. Cut a hole slightly smaller than 1/2 inch in the lid so that the 1/2-inch tubing makes a snug fit. Put the lid on the container and push the 1/2-inch tube all the way down to the bottom of the container. With a heated nail or a drill, make a bunch of small holes in the remaining area of the lid.

4. With a heated screwdriver or a drill, make a hole in the side of the 1/2-inch tubing for the airline tubing to fit. Again, the hole should be slightly undersized for a tight fit. It would probably help to make the hole at an angle, since the airline will be coming in at an angle. Also, when making the hole, it is good to leave yourself some room (1/2 inch) between the top of the lid and the bottom of the hole. This will make the canister easier to fill with media later on.

5. Press the airline tubing into the new hole, and push it about halfway down into the canister. You don't want air bubbles to find themselves going back through the media the wrong way.

6. Now, unsnap the lid and swivel it out of the way, as you keep the 1/2-inch tubing all the way down to the bottom. Fill the rest of the container with zeolite or the media of your choice. You should be able to get a few tablespoons of media into a film canister. Carefully snap the lid back on and hook the airline tubing to a small air pump.

The whole thing costs practically nothing beyond the media and the air pump. If you have a few tanks you probably already have all the materials laying around.

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.