Reptile & Amphibian Forums

I have a 7-8 litre tank which is small and it needs a filter fast as it always needs cleaning. My preference is to have a small external filter as i hate internal filters and they won't really fit inside the tank. Also has anyone got any plans for a filter that doesn't run by electricity as that would be helpful.

if anyone has any plans as i have tried to make one and it wouldn't work so please could anyone help me!!!!

I would also like to know whether you can make an external filter with a air pump instead of a water pump?? if anyone knows then please tell me how to do so!!

Well, for an external filter, you would need a U shaped pipe to draw the water out of the tank, and into your filtration system.

Then you would need a waterproof box of some sort, and either a lip on it, or a funnel sort of attachment, to let the water go back into the tank.

Most external filters put their motor right below the U shaped tube, to suck the water in, and through the various filter media.

Air powered filtration systems usually have an air pump, a thin air tube, and a bubble stone beneath an uplift tube. The bubbles in this tube cause the water to rise along with them.

You can't put the air tube into the U shaped tube, because the bubbles would block the tube at the elbow. I suppose you might use a J shaped tube, but I don't think the bubbles would push the water hard enough to get it over the lip of the aquarium. Thus, you would probably need to put an uplift tube in the filter box itself. However, external filters generally need to have their water level a good deal higher than the water level of the tank, so unless your air pump has the strength to power a small sauna, I don't see how it would work.

I'm also a little confused about a pump "not run by electricity" Are you hoping to have the movement of the water in the tank power it, as a perpetual motion machine?

I guess a powerful clockwork spring, or some massive counterweights might be pressed into service, but this would require specialized watertight fittings, unless you want to run a belt into the water, and back out...

I dunno about the motor. Most of the professional filters just have a sort of paddle wheel, so I guess it's not too hard to make. For the housing, I suppose you might press an old cardobard milk carton into service, and a snorkel might do for the U shaped tube.

Pet stores generally have pretty cheap stuff, I've seen a few nice off the shelf extrenal filters that'd work pretty well for a few gallons, and by the time you factor in materials, and time, you may do better that way any how.

OF course, that wouldn't be DIY.

Well, I won't dare say that I'm a pro at this sort of thing but after a sponge filter didn't work out for me (about $14 down the tube) I decided to create my own filter. The first edition of it is making a test run right now in a ten gallon tank. I used the old tubing of the sponge filter (which included a small weight, a hard plastic tube and a thinner curved tube that sits in a hole on the side of the larger tube), a 8oz yogurt container with it's lid, a pair of nylons and some carbon. Like I said, I'm not too sure this set-up is going to be the greatest, but I'm testing it as I type.
What I did:
Cut a rectangle hole in the top of the yogurt lid with an exacto knife to insert tubing. Put the tubing throught that hole just so you can get the weight reconnected. Cut off one foot of the nylons and save the rest for later. Put the carbon into the foot of the nylon and tie the top so it makes a sausage like shape. Rinse the carbon dust and wrap the sausage around the weight. This (I'm hoping) will make a small carbon filter. Poke holes around the sides of the yogurt cup and attach the lid (with filter) back onto the container.
It currently takes up about three inches diameter of my tank and seems to keep the water fresh smelling so far. And to make it cost even less you could get the weight and tubing from any hardware store. Hope this helps.

without all the various components of filtration, here is the basic problem you need to solve. how to get water from the tank to an external container, and how to get the water back to the tank.

In my opinion the best way to do this is to have your external container level with the aquarium, and a siphon connecting the two. This will connect the water of both tanks. If the water in one tank increases or decreases, so will the other.

If you insert a small water pump in the external tank, and pump water back to the main tank, as the water level decreases in the external tank, water will start moving through the siphon thus keeping both tanks level.

The diagram below shows the basic idea.

Now all you need to do is put your filter media between the siphon and the pump, and you have yourself a very simple filter.

The advantage to having the pump after the filter is that it is much less likely to clog as only filtered water will enter it.

You could put the pump in the tank and have the siphon to return the water, but you would be cleaning the pump regularly.

There are many variations of this basic setup. If you would like more help let me know, I usually check this forum about once a week.