Today I want to share how I utilize air lifts in very shallow tanks (less than a foot of water). Since I have talked about airlifts in a previous post on oxygen, I won't reiterate how they work or why you would be interested.
Air lifts in shallow water present a unique problem because they really don't want to stand up straight. In addition, they are so small and wobbly that the stiff 1/4" drip line we use to supply air pushes them around.
Solving this problem requires that we stabilize the base of the air lift so we can put weight on it. Unfortunately we really need the top of the air lift to be narrow so that the water is forced out of the top with the air. Here I am using 2" or 1-1/2" pipe with fittings to attach a short 1/2" pipe with a 90° fitting on the top.
Next we need to cut some slots in the base so that when it is standing on a flat surface it can still suck in water. The larger these cuts the better, but make sure you leave at least an inch of space between the cuts and the water line for your air inlet. Next measure a rough inch from the top of the cuts and drill a 1/4" hole for your air line. Be certain the air line is under water.
Finally, we need a way to hold the air lift in place. It needs to be heavy, but not leach anything into the water. That doesn't leave a lot of options, with rock being the cheapest. Originally I tried tying a large stone to the base of my air lift, but that was quite difficult to accomplish with a satisfactory result. As you can see in these pictures, I finally settled on pouring 3/4" river rock over the base of the air lift. This not only gives the air lift some weight, but it also helps keep the air line in check and provides some nice space for bacteria with a good flow of water.
Here you are looking at an operational air lift in a juvinile crawdad tank. This tank has just about 6 inches of water to keep them from crawling out, along with some pipe so they have a place to call home.