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I used a Rubbermaid 70 gal stock tank because it was readily available at a local hardware store. It had a 1 1/4" bulkhead connector at the bottom, but I replaced it for two reasons. First, it was cracked and leaked. Second, I needed 1" plumbing. The bulkhead connector I used (#BKF13) is threaded on the inside, so I could easily fasten a strainer (#CV2S) on the inside and a coupler for 1" PVC on the outside. I wanted threads so I could easily disconnect the plumbing from the tank if I needed to.

The 1" expansion coupling was used for two reasons. First, I wanted to be able to rotate the upper plumbing assembly for easier filter change. Second, It allows about 1 and 1/2 inch up and down travel to better control the tank water level.

The upper 1" ball valve is threaded for ease of maintenance if needed. I use the valve to control the water flow rate to the system at approximately 70 GPH.

The lower ball valve is glued in. It's purpose is for draining the tank or just making partial water changes. I used the left over 3/4" flex PVC to route the water out of the greenhouse. I also found that the drain output should be glued in at about a 30 degree angle. It makes it a lot easier to fasten the flex PVC to the 3/4" barb.

You will need a few short pieces of 1" PVC to connect the plumbing components together. I didn't include it on the parts list because all you need are a couple of scrap pieces. Don't forget to tape all threads. I would glue all slip connections except the piece of pipe from the filter to the bed.

I used plastic pipe strap and a couple of small bolts to fasten the return line to the top of the tank. A 3/4" end cap with 8 or 9 holes 1/8" drilled in it was glued to the return line. I would suggest using a barb connector and a screw-on cap. With the cap glued on you can't clean it if it gets garbage in it.

I used a five gallon bucket with a screw-on lid for the filter. Cut a 6" diameter hole in the lid so the filter bag will sit in, but not fall all the way in to he bucket.

The filter bag I used (#FB100N) is a nylon mesh bag 7" diameter by 32" long with a 7" polypropylene ring in the opening. The bag is over twice the length needed, but the price was right. I figure I can sew it and cut it off if I want to.

I used a 1" bulkhead connector (#BKF10) about 4" down from the top of the bucket. It has a slip fitting, so a 1" PVC pipe just slides in. Don't glue this connection unless you have to. At the other end of the PVC pipe I slipped on a 1" elbow and set it into one of the net cup holes in the blue board.

I used a 18" x 24" piece of 1/2" plywood between the bucket and the cement blocks. This height will vary depending on the height of the bucket and where you place the bulkhead connector. This is a gravity feed system, so everything has to flow from the fish tank to the grow bed without overflowing or blocking the flow. The plywood also makes a nice little table for things like a small air pump or whatever. I installed an air stone in my fish tank to compensate for the low DO caused by high water temperature and high pH.

I made the grow bed 3' x 8' x 8" outside dimensions. I cut a 3' x 8' sheet of 5/8" plywood and screwed on 2" x 8" yellow pine boards. Then I measured in about 11" from the end and drilled a 1-3/4" hole for the drain.

The liner I used is black fish grade 30 mil vinyl. It was very stiff and hard to fit to the corners. The vinyl really didn't lay in well until water was added later. When sizing the liner, add 2' to the length and width of the bed. In this case the liner is 5' X 10'. Center the liner as best you can, then take a sharp knife and cut an "X" where the drain hole is.

I used a 1" bulkhead connector (#BKF11). It has a slip fitting at the top and female 1" threads at the bottom. Use a little aquarium seal on the gasket and slide the bulkhead connector down through the hole from the vinyl side. Don't forget the nut on the bottom side like I did! In the top of the connector, I just pushed in a 6" piece of 1" PVC pipe to regulate the water height in the bed. On the bottom of the connector I screwed in a 1" male barb adapter for the 1" drain line to the return tank.

I filled the bed with water to just below the top of the drain pipe, then smoothed out the vinyl and shaped the corners as best as I could. To hold the outer edges of the vinyl, I Just tied a 1/4" nylon rope around the outside of the bed. I added 5 gallons of washed pea gravel to the bed to give the bio-filter a little more surface area.

The 1.5" blue board I purchased was already scored at 32" so I just snapped it off. I used a sharp butcher knife to cut the length to 92". Because of the folds in the liner at the corners, I used a hack saw and rounded the corners of the blue board. The diagram above shows the drill pattern for the 1-3/4" holes.

After drilling the holes I placed the blue board in the bed, centered it, then pressed it down on the drain pipe to mark it. I then removed the blue board and cut a fairly large hole for the drain. After drilling it with the hole saw, I enlarged the hole with a steak knife.

I didn't paint the blue board, but I believe it is recommended to extend it's life.

I used a 10 gallon rubbermaid tub with a lid for the return tank. It's 16" high so it fits nicely under the grow bed.

I'm planning to build a larger system, so for standardization I used a 1/2 HP sump pump with a float switch.

I started by using a 1-3/4" hole saw to cut 3 holes in the lid. One at one end and two at the other. I used the single hole to feed the 1" tube from the grow bed. The other two holes are for the 3/4" flex PVC line from the pump and for the by-pass back to the tank.

For this small system, a 1/2HP sump pump is a lot of over-kill. To reduce the water pressure at the fish tank without loading the pump, I added a bypass in the return line. I used a 3/4" T adapter, 3/4" ball valve (threaded), an L adapter and a short piece of 3/4" flex PVC. The bypass plumbing was placed outside of the tank for ease of adjustment.

I used a couple of pieces of plastic pipe strap and screwed the return pipe to the bottom edge of the grow bed.