The last water test I did was strongly suggesting that I need to add another growbed to this build, and I’m not really surprised with that. The fish load is fairly high for the growbed area, and I have to do a partial water change about once a month. On the other hand, the water that comes out is used for the houseplants and Chrissie’s Bonsai work, so it’s not a loss. For a bit of extra safety, though, I keep a pair of air stones bubbling in the tank.

That system was built out and put into service at the end of September, 2020. In January, 2021, I started setting up the smaller system in my office.

The Office system is 210L, again, using a livestock tank for the fish. A filter box encloses the pump, and contains two grades of mechanical filter media, as well as several 30mm “Bio-Balls“. Water flows up via 25mm SCH40 PVC pipe to a T-Joint and ball-valve.

The path of least resistance is to a 25mm drop pipe that occupies the first ⅛ or so of the distance back to the water. Surrounding that, and reaching all the way to the just shy of the water’s surface is a 30mm pipe. That long drop ensures a lot of good aeration of the falling water as well as substantial surface agitation. I call that the “return drop shroud”.

The path of most resistance leads to a 25mm/12mm reducer, which then goes to a 12mm barbed fitting. A short piece of clear 12mm plastic hosed is fitted over the barb, with the other end crimped shut. A “vampire” drip emitter pierces the hose, and leads to a 3mm / 8L/h aquarium hose, which in turn empties into the top of what is currently a singular ZipGrow 1.5m Tower.

Water slowly(!) trickles down the mesh media inside the ZipGrow tower, and keeps the roots of the plants moist and furnished with nutrients. Obviously, the mesh also does some mechanical & biological filtration, but a 8L/h drip, it’s more than a day to have any effect on the water quality. The primary filtration is the pump box I described above.

I have two more of the towers, and once I’m happy with the plumbing config & water flow, I’ll be adding them in, one at a time. So far the Sweetpeas adore the environment and are going to require stringing to keep the runners in sane management. The Chard and the Phlox Ground Creeper are also both looking pretty healthy.

Mathematically, at 4L/h, I’d need 25 or more towers to properly utilize the total nutrition in the system and run the biology properly. That’s just not going to happen in my office. So, after a bit of other work happens in the office, I anticipate putting a couple of citrus trees into this system, using “Bucket In Bucket” with an external flood-and-drain siphon. That will help with managing the water quality.