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 just one example of how to build a bell siphon.
To start, assemble 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.
Showing where the tub will go.
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.
The bottom half of the bulkhead and the 90 degree angle. The angle will provide the offset to go around the tank lid.
A bit of glue oozing into the joint. This needs to be cleaned out to provide less water flow resistance.
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.
Oohps! I cracked the bottom of the grow bed. No worries, a bit of silicone will fix it right up!
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…
The stand pipe drain assembled and ready to seal in place with silicone
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.
The notches in the bottom of the bell siphon allows water to flow in easily.
A slight design flaw (uhm, 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 grow bed sitting on the aquarium light hood.
The canister filter has nearly filled the growbed. The water height is limited by the height of the stand pipe.
The bell siphon sitting on top of the stand pipe. This is where the magic happens.
Looking at the whole bell siphon drain.
The threaded bottom allows me to potentially change how I drain this grow bed if I wanted to.
The growbed is continuously filled, and intermittently dumps into the aquarium below.
The water from the grow bed returns back to the aquarium here. The grow bed is still filling in this photo.
Bell Siphon draining into the aquarium. See all the water flowing out?
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.
I only have desk lights with CFL bulbs right now. I think it looks pretty good!
The tank looks good with the aquaponics on top!