Modify a Marineland brand "Eclipse" fish tank filter to be a mini plant cloning unit.*
For this mod, you will need a hack saw or jig saw to cut a hole in the lid, a bag of filter floss, a pair of scissors, and two foam sponges. You will also need two light fixtures and compact florescent bulbs to give your cuttings adequate light. If your tank is in bright light you won't need the fixtures, but keeping a fish tank is bright daylight promotes lots of algae growth.
*This instructable will show you how to mod your filter, but does not cover how to set up or maintain a home fish tank.
Step 1: Aquire an Eclipse Filter
The Marineland brand Eclipse filters are common "all in one" filtering and lighting systems for aquariums. They can be found used on eBay or possibly in a local thrift store. They are also readily available online. I already had one on my 20 gallon fish tank, and liked it, but did not want to keep buying the filter cartridge replacements. So I now use plants to clean my water.
Step 2: Remove the Filter Cartridge and Lid
First step is to open the lid and remove the blue filter cartridge. Next, slide open the two tabs at the back corners of the lid and lift the lid out.
Step 3: Mark and Cut the Hole on the Lid
Use a marking pen to trace out a U-shaped hole in the lid that will give you access to the tray that holds the filter cartridge. This tray will hold your clones. You want to cut out a hole that allows access to the entire tray but still covers the pump inlet on the left and the biowheel on the right.
Now use a jig saw or hack saw to cut out the hole you marked.
Step 4: Replace the Filter Cartridge With a Shallow Bed of Filter Floss and Sponge
Now that the tray is empty, you can fill it with a small amount of filter floss. This is the white fluffy stuff sold in fish stores that filters particulates out of aquarium water. You only need a layer about 1/2" thick. Have the filter running when you do this so you can get it wet and that will make it easier to get it in the tray nice and evenly.
Next, take your two (or more depending on your model of Eclipse filter) foam sponges and cut slits from the long edges into the center. These slits will hold your cuttings upright. Place the sponges into the tray on top of the filter floss.
Step 5: Replace Lid and Add Plant Cuttings
Replace the lid and secure by sliding the tabs into place. Now you can take a few cuttings and slide them into the slots of your sponge. Be sure the end of the cutting reaches down into the wet filter floss. Experiment with different types of plants. Spider plants can grow quite large in the this set up so be prepared to cut them back or divide them. I have had success with lavender, mint and rosemary, too.
Step 6: Mount Your CFLs
Next, be sure to give your cuttings the light they need to thrive. I used two 9 watt bulbs in clamp fixtures with metal reflector shades.