I had a rough week this last week, so I decided I needed to build something. So I built a bell siphon for an ebb and flow grow bed (also called Flood and Drain grow bed_ for the 75 gallon fish tank in the living room. This will allow me to grow plants using the fish water. This is pretty cool, as it means that the plants will remove the nitrate buildup which is the primary reason people need to do partial water changed in their aquariums.
The whole thing will be completely automated and cost me less then $50 including buying tools and leaves me with lots of spare parts. 3 pieces of 4 foot PVC pipe with only about 6 inches cut off of each, so I have enough of this to make half a dozen more if I wanted.
A bell siphon is a passive autosiphon device that allows a continuous flow of water into a container to periodically be drained completely out of the container. This is good because it allows me to have my Eheim aquarium canister filter output into the grow bed, and the bell siphon will flush the bed regularly, aerating the plant roots.
To start, I assembled a drain out of plumbing PVC parts. This consists of a stand pipe to go inside the aquarium, 2 fittings to work as a bulkhead nipple, and an offset to route the water around the aquarium lid into the drain tube.
My wife let me buy the parts and take over the 75 gallon aquarium in the living room with my plants. She had it decorated really nicely, but my plant stand was evicted from its spot to make space in the baby room. They needed a place to go, and I used this as an excuse to work on the aquaponics setup.
I started fiddling with the pieces I had bought and realized that I didn’t get all the right pieces I wanted, but I had gotten enough to make it work.
I used an antique brace with an adjustable size bit to cut the hole in the plastic. Basically, the edge of the bit would score the plastic. It worked great, except for the plastic cracking. I siliconed it up, but, to my great annoyance, the silicone was old and didn’t set. I had to clean it off and go get a new tube and try again.
After two days of futzing with this thing, I finally got a dried silicone seal around the stand pipe and over the crack. The grow bed will sit on top of my 75 gallon aquarium so I designed the drain to offset around the aquarium lid. No drilling holes in the lid… yet…
I then made the bell siphon which sets over the stand pipe. I again used my brace and a smaller bit to drill holes in the 3″ PVC pipe. This made it much easier to cut with the PVC cutters I had bought. The 3 inch was just to thick for me to cut otherwise.
A slight design flaw (um, the drain) left me with a grow bed that wouldn’t sit on the aquarium stand lid. A bit of scrounging around, and I found a plastic crate that I am using. The grow bed sits on the crate, which leaves enough room underneath for the drain to fit. It looks a little precarious, and I would like it to be the 4-5 inches lower, but it works for now.
The growbed is continuously filled, and intermittently dumps into the aquarium below.
I placed my plants around the grow bed and the few items that where required to stay on the tank stand – family photos. I think it looks pretty good in the house! I hope to grow lettuces and herbs such as basil in it. Things that we eat regularly and are best fresh.
You can visit http://mike.creuzer.com/2011/12/i-doubled-the-sump-space-in-my-aquaponics-rig-today.html to see this same siphon and growbed in use on an expanded system.