Grow bed plumbing
There are several different methods on how to add and drain the water to and from your grow bed.
A very common one is referred to as an “Ebb & Flow” method. In this method a water pump is used to pump the water from the fish tank into the grow bed continuously. A “bell siphon” flushes or drains the water rapidly, once it reaches the desired fill level in the grow bed. Then the process repeats. A modified version of this uses a programmable timer to only fill the bed a few times per day.
A better mousetrap
After looking at what other “aquaponists” have come up with, I decided to simplify things. I had come across a lot of YouTube videos in which folks had issues with bell siphons. I figured, for what do you need a bell siphon? If the pump transports the water into the grow bed, why couldn’t I also drain the water back into the fish tank via the same path? That would eliminate the need for the bell siphon and a potential maintenance and point of failure in my system. Additionally, my pump has a foam filter. Using this back flush method should theoretically backwash my filter after each filling operation and thus reduce the need for me to clean the filter – genius! 🙂
So far, this setup has worked for me very well. The bed doesn’t drain rapidly as with an auto-siphon, but that probably doesn’t matter that much. The bed fills from the bottom up, right about 1/2″ inch under the top layer of the growing media. This avoids algae growth and too much evaporation.
All I had to do is the following: I added a bulk head fitting to the grow bed. It has a barbed hose fitting pointing down to the fish tank. I connected the hose coming from the pump to it. I added a second bulk head fitting with an extended pipe reaching into my grow bed. This is an overflow, in case the pump does not turn off. Unfortunately, I did not take a photo of this. Imagine two holes cut with a hole saw into the center of the grow bed to the left.