In my previous article, I discussed the basics of how I have turned my 90 gallon Freshwater tank into an aquaponics system. In this post we’ll take a deep look at how I turned a rather boring sump/display setup into a vegetable-producing powerhouse.

To get started, let’s bring back the rough diagram from the last post of how my aquaponics system is set up:

Today, we’re going to focus on that “Grow Beds” bit in the diagram from start to finish — from the moment the water leaves my display tank upstairs, until it ends up back in the sump to be cycled back upstairs. Between these two points, we have a lot going on:

We filter the water for larger particles that might cause nasty clogs in your system

We feed 4 individual home made grow beds using an ebb and flow system implemented via bell siphon

We collect all the water from the grow beds and feed it back into the sump to cycle again

First, let’s start with the framing. For my setup, I used two large heavy-duty steel shelving units to house the entire setup. Remember water is heavy (about 8 pounds per gallon), and more over the odds the framing is going to get wet over time are pretty high — so going with strong steel supports is a very good idea. While not the exact same product as I used, units like these should give you a good idea of what I would recommend.

When the water first leaves the tanks and travels along the return plumbing in the house, the first stop once it reaches the basement is something called a Swirl Filter (I’m sure it has other names as well). So what exactly is a Swirl Filter? Let’s take a look!

As it’s name implies, a Swirl Filter is a Filtering mechanism that is used to filter out larger particles of stuff in the return water through centrifugal force. Here’s a picture of roughly how one of these things are constructed:

As you can see, basically a Swirl Filter is a container you fill with your water (in this case, from my display tank) that has a few different drains in it. In the center of the container we have the primary drain, on the left with have a safety drain (which is oriented higher than the primary drain), and finally on the right we have our input supply of water coming from my display tank toward the edge of the container. You’ll note that the input supply of water does not simply drain into the container, but has a 90 degree at the end directing the water toward the edge of the container instead. This is very important to how this whole system works, so let me explain.

The way a Swirl Filter works is basically by creating a circular current in the container. As the water rotates around the center (where the drain is), particles are naturally pulled toward the edge of the container — leaving the water in the center to drain without any particles. For most things, eventually the particles settle in the water at the bottom of the swirl filter which can then be drained (by installing a valve that drains water from the bottom of the filter). This is why the 90 degree exists, because once the container fills up to the height of the primary drain, it will start causing the water to swirl around the container creating this force. The result is water with less gunk in it to clog things up further down the line when the pipes are smaller.

As a safety precaution we add a second drain. This drain’s high water mark is higher than the primary drain and is designed to only be used if, for some reason, the primary drain doesn’t actually drain and the water level starts to rise in the filter. If that was to happen, the secondary drain will start draining the water instead. In my case, the secondary safety drain goes straight back to the sump using a big 2″ pipe (thus I am reasonably assured I won’t ever have a flood from the filter).

You can build a swirl filter out of pretty much anything you want, in my case I used a regular old storage bin with some of these great uniseal adapters. Remember, when drilling out holes for the pipes to use masking tape to make sure you get a nice clean cut without any fractures or cracks! Here’s my swirl filter, the first stop as the water flows out of my display tank upstairs:

Important: When choosing a container, remember that this container’s material will be indirectly exposed to both your fish and your food! In my case, I used Polypropylene containers, but it’s up to you to make sure you do the homework here to avoid introducing harmful chemicals into the water supply!

In the pic you can clearly see the primary drain (leading to my grow beds) on the right, the secondary safety drain at the top front, and a “cleaning” drain at the bottom front that has a valve on it I can use to drain the gunk from the bottom of the filter with as it settles.

Now, onwards to the grow beds!

In the last article we discussed how each grow bed implements an ebb and flow drainage system through the use of Bell siphons. Let’s dig into that a bit more and show you actually how those were built. For the beds themselves, I used standard low-wall storage containers. For each container, I cut a hole in the center and installed a standard aquarium bulkhead (like these) and drilled a corresponding hole through the shelf the grow bed rested on. On the underside of the shelf I installed a 90 degree PVC joint off the bulkhead, and plumbed the drain for the grow bed into a central drain pipe that leads back into my sump:

With the drain plumbed, it was a relatively straightforward process to plumb the input water supply. In my case I simply used a 1 1/2″ PVC leading from the primary drain of my Swirl filter, with a PVC T joint leading to a valve for each grow bed. Doesn’t really matter where in the grow bed you put the input water valve (although I certainly recommend you install one, so you can shut off a bed’s water supply to perform maintenance).

Now to construct our Bell siphons for each grow bed. This is pretty straightforward as well, just a length of 1″ PVC. The height of this length of pipe depends on the height of your grow bed — you want it about 1/4″ lower than the height of your growing medium. When considering this height, keep in mind it determines how high your grow beds will fill with water before they drain — if you cut it too close you’re likely to end up flooding sooner or later!

Over the grow bed’s drain pipe is a larger PVC pipe with an endcap that serves as the “bell” portion of our Bell siphon. The base of this covering I cut out notches to allow water and air to flow in as the siphon engages and disengages. Finally, we install an even larger PVC pipe section with a bunch of holes drilled into it to serve as a barrier between the bell siphon and the grow medium around it. The holes obviously should be large enough to allow water to easily flow, but small enough to keep the grow medium (clay pellets, whatever) from getting into the mechanism.

Here’s an example of how the grow bed will look once you’ve added the grow medium (In this shot I used another small plastic container as a place to store new seedlings I’m growing in the system):

As a final note, when I first built my system I terminated my water input coming from my Swirl filter with just a regular PVC end cap. This worked fine, but as any plumber will tell you, it’s going to cause a LOT of gurgling as air is forced to escape the system through the outputs of the grow bed valves. The solution to this is to instead install additional plumbing at the end of your system with a T-joint that allows excess water to drain back into the sump while at the same time allows air to escape through a vent plumbed into the top of that T. It’s not really “necessary” to make a functional system, but certainly a quieter one!

That’s it, now all you need is to start planting things and install some suitable lighting. Don’t want to spend a fortune on that? Check out my article on building DIY aquaponics light fixtures you see in the various pictures of my setup.

Until next time!