My reason for building this project was to get practice and learn about any problems that will come up before making a bigger system.
Step 1: Get Materials
-Steel cart and some steel bars
-Plastic bins that cover about the same area as the cart
-Larger, deep plastic bin
-Water pump with a roll of tube that fits it
-Bag of pea gravel
-Gallon milk jug
-Whatever type of fish and plants you will want
-Hot glue gun
-Water proof glue
-Knife or scissors
Step 2: Make the Skeleton
Once the frame is made cut and attach the milk container. Cut across the handle, cut a big opening in the handle side, and cut a small opening near the top of the other side. This will be a funnel for the water coming out of the grow beds. Attach it to the frame with a zip tie through the handle and around the steel bar.
Lay the plywood pieces on the horizontal steel bars. These will support the cat litter boxes.
Step 3: Make the grow beds
Cut the plastic colander into fourths. Glue 1/4 of it over each of the two holes in the grow beds to keep the gravel from flowing out the hole. You don't need the rest of the colander.
Support the back of the drain funnel with zip ties from the corners of the grow beds.
Wash the pea gravel with water and put it in the grow beds. Then rinse it more until the water coming out is clear.