Detail © David Hynds
Tired of that ugly sponge filter in your otherwise gorgeous aquarium? Here is an easy DIY project that will conceal the filter and enhance the aesthetics of your tank.
Sponge filters are popular for small tanks like hospitals or breeding tanks. They also work great for fish which prefer the surface of the water to be calm. Beneficial bacteria grow on the sponge and clean the water. The problem is that sponge filters are almost always bulky and ugly. A coconut shell is perfect for adding to the atmosphere of your tank while hiding that awkward, unsightly sponge in the corner.
For this project you will need: 1 coconut, a hammer, a drill, an ice-cream scoop or sturdy knife, a deep pot to boil water in, 6” length of 3/4” plastic tubing, a cap for one end of the 3/4” tubing, 4-6’ air line tubing and an air pump, a nail, aquarium-safe silicone, and an open-pore sponge.
First, buy a coconut. The ones available at the grocery story are often scored, so they crack open easily. Find one of these, if possible. On the top of the coconut, you will find three indentations where the coconut was attached to the tree. Poke or drill through the largest of the three holes, and drain the milk. Using a hammer, crack the coconut in half. Don’t be too zealous in your hammering. You just want to crack it in half along the score marks, not obliterate the shell. It usually works best if you just tap it gently until it cracks enough that you can pull it apart with your hands. Scoop out the meat. An ice-cream scoop usually works best. A knife with a thick, short blade also works well. You want to get between the meat and the shell, and pop the meat out.
Boil the top half of the coconut to kill anything potentially harmful and to keep it from leaching much tannin. Boil it for 15 minutes, empty the water and refill it. Do this again twice for 30 minutes and then again for an hour. The coconut may turn your water a little brown when first introduced to the tank. The tannins it leaches are mildly acidic and may affect the pH slightly.
While your coconut dries, heat the nail, and use it to poke holes in the bottom inch 3/4" outlet tube. Next, glue the air line tubing to the inside of the outlet tube. You want the end of the air line tubing to be just slightly above the holes you poked with the nail. Next, cap off bottom end of the outlet tube. Take your sponge and cut a 1" deep hole down into it. It needs to be deep enough to cover all of the holes in the outlet tube. Insert the bottom of the outlet tube into the sponge.
Use a drill to enlarge the hole you made to drain the milk. Make the hole big enough for your outlet tube to fit snugly inside. Put the air line and outlet tube through the hole, so that they are sticking up out of the top of the coconut. Put the coconut into your tank, hook up the other end of the air line to the pump, and turn it on. The coconut should be heavy enough to make the whole apparatus sink. If not, simply glue a few rocks or marbles to the inside of the coconut until it sinks.
This project is easy and inexpensive. The coconut will really enhance the appearance of any tank. You can even use the other half of the coconut to make a cave. Your fish will love it, and so will you.