A simple way, to use those air pump, is to make a simple drawing filter
here are the steps, Simply said
1, find the sponge, (fishtank sponge, not biodegradable, or dishwashing sponges)
2 Freeze the sponge in a bath of water.
3 find the tubing, for the drawing shaft. you can use, PVC, or the clear tubing found in fish tank stores.
4 drill many little holes, make sure you put enough and that they aren;t crazy small, but not to many. for each inch (that will be covered later with the sponge) drill about 12 HB pencil size holes.
5. get your frozen sponge and drill a hole in it the same size, or slightly smaller then the drawing tube.
6. Plug the end of the tube and feed it into the now thaw sponge.
7. get your self an airstone and some air tubing. put them into the draw tube.
8. submerge and try to squeeze out all the air from the sponge.
9. turn on the air.
NOTE: the size has to match the air pump. its kinda trial and error with a touch of logic. don;t use a basketball size sponge with a tiny airpump.
The draw tube can be completely submerged or slightly past the surface, but it can;t be to high out of the water, so cut that tube accordingly
This is how I have made undergravel filters. Materials: calking tube of Silicon and applicator(calking gun) piece of plastic flourescent light fixture cover. The "grid" that has
1/2" square holes in it. Purchase at Lowe's or scrounge if small size tank. The taller you make it the more space in the tank it takes up. You can make it to fit two ways.
Hidden or not. Allow yourself 1/4" and measure the inside of the tank wall to wall front to back. If you want hidden make the measurement 1.25" less from front to back.
If not hidden full measurements. I don't know exactly what size they are but marbles about 1/2" are needed. This makes it short but I use PVC 1/2" pipe couplings.
If using marbles place the grid on table and using a generous dab of Silican on each marble place then 1" from the edge of the grid and aprox every three inches front
to back and side to side. If you vacuum your gravel it's not important but if not you need a center divider under the filter. So don't put marbles directly in a line from
back to front down the middle. The divider is cut glass as long as the grid is from front to back. But you can't get it till you know exactly how high this is. I use 1/2"
PVC pipe couplings for this because the people at the glass place look at you funny if you say you want an 8" long piece of glass 1/2" wide. You don't need this at
all if you vacuum the gravel though. Buy a piece of fiberglass screen wire large enough to cover the tank. Place the grid down on the floor of the tank/w the marbles
down. if hidden push it to the back of the tank/w the space along the front void of the grid. Cut the screen to fit the inside of the tank. If hidden cut it long enough
from front to back that it can go down the front of the grid and across the floor to the front of the tank. Gravel will fill this space and hide the filter. You can silicon
around all edges of this. Now for the discharge tubes. BTW you can clip off the corners of the back of the screen about 1" where the discharge tubes go. One word
about this however. My Khuli Loach lives in my filter till he's ready to come out to get food, usually at night. Other fish the size of Platty's can/will go down through
there if you cut the corners off the screen and sometimes die down there.
The discharge tubes are cut glass (I prefer 1/4" to give the silicon something to cling to better) and are aprox. 1.75" wide by the distance from the top of your
now installed filter plate to 1/2" or as much as 1.25" from where you want the water level to be in the tank. 1/2" makes it harder for fish to "find" it and larger gives
more flow. You need to cut a piece of whatever that length to put it diagonally in the corner to make sure that your bubble stone fits past it and adjust the width
accordingly. This glass fits diagonally across each end forming a triangle in the corner that runs from the top of the filter plate to the desired height. I find it best to
keep the water level at least 1/2" below the top rim(outside bottom of the top rim) for these filters. When you have made sure your stone will fit down this you can
silicon each piece in each corner seperately placing the side of the tank down on the table to do this and let stand for one day and do the other corner then.
After proper installation you should not see anything but the discharge tubes going from the bottom of the tank to the top (just below the water level in each of
the back corners) unless you have opted to have it not hidden in which case you will also see the front edge of the filter plate and under the filter also.
You can easily tell when your gravel needs vacuuming by the action of the bubbles in the tubes. They flow freely when it's clean but swirl around when it's
beginning to clog. Do NOT use sand for this filter. It likes gravel. The size that Walmart sells is too big. You need smaller than that.
If I have not given clear directions for this you can e-mail me or just post a question/w this filter description.
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