Aquaponics is using fish waste to feed plants. In turn, the plants help clean the water the fish live in. This system works by pumping water from a fish tank through a grow bed, then letting gravity draining the water back into the fish tank.
I've wanted to get into aquaponics for a while, so I finally took the leap. I built a small system for fairly cheap. It's not going to be feeding my family anytime soon, but it's been great to learn on. It's pretty self contained and sits nicely in the corner of my garage.
Step 1: Prep the Containers and Shelves
First, let's get our little unit ready for the plumbing.
I wanted the system to stand on it's own, so I bought a shelving unit to place the grow bed and fish tank on.
For the fish tank, I grabbed a 20 gallon rubber tub
My grow bed is a large mortar mixing tub
The mortar mixing tub is slightly longer than the rack, so it won't fit without some modification. Luckily, the posts of the rack sit right on the lip of the tub, so drilling four 3/4" holes is an easy fix. This also makes the grow bed sit nice and secure on the rack.
The other hole you'll need is where your siphon will drain out. Drill a 1" hole somewhere on the base of the mortar tub. Do this after you drilled the post holes, and make sure it lines up with the space between the bars of the shelf it will be sitting on.
Step 2: Build the Siphon
The next step is the most intricate part of an ebb & flow system. This will allow the grow bed to fill slowly, then drain quickly. Once we introduce the timers, this process will happen automatically.
- 3/4" electrical watertight fitting
- 3/4" PVC pipe
- 1" to 3/4" PVC reducer (my Home Depot didn't have this piece, so I used a 1" coupling and a bushing)
- 2" PVC pipe
- 2" cap
- PVC glue
- 4" PVC
Take some measurements to determine the height of your siphon. You'll want the water level at least an inch below the top of your grow bed. In my 7" deep bed, I cut my PVC too long. I would recommend using a 4" pipe length to attach the fittings to.
For the bell, cut a length of the medium diameter (2") pipe that is a matching height to the siphon. Slide the cap on to, but don't glue it. The pressure of the siphon will be pulling down, so there's no need for the glue. You'll be making some adjustments to make your siphon work right and being able to pop the cap off to take some length off is easier than taking it off the bottom.
Cut a length of the 4" PVC pipe that is the full depth of your grow bed, plus a little. This will fit around your bell, with space to spare, keeping your grow medium away from the bell and siphon.
In the bottom inch of both the guard and the bell, drill a grid of holes. This will allow water (but not grow medium) to flow into the siphon. The height of the holes on the guard matters less, but the height of the holes on the bell will determine when the siphon breaks. Putting them an inch high allows a bit of water to stay in the bottom of the bed.
Once assembled, test your siphon. Screw on the bits of the fitting and fill the grow bed with water. Without the grow medium, the grow bed holds a ton of water. However, it's still worth it to make sure your siphon is at the right height. Mine wound up way too high, and taking height off it at this stage is much easier than later.
Step 3: The Rest of the Plumbing and Lighting
Now that we've got the siphon working, let's get the water flowing in and out of our grow bed and fish tank reliably.
- 5 x 3/4" PVC elbows
- 3/4" male adapter
- Aquarium pump (http://tinyurl.com/ohyultc)
- 3/4" ID flexible tubing
- 2 hose clamps
- Female tubing adapter
- Grow lamps (http://tinyurl.com/lhemd4b and http://tinyurl.com/lwwgobu)
There are a lot of options about how to deliver the water and how to have it return. I decided to keep it minimal and build some piping the came up around the outside of the grow bed. Since my siphon is so near the edge, I wanted to move the water back to the middle. Keeping the drain exit high above the water allows the water to fall and splash, keeping the DO levels up.
The pump I got is far too powerful for this small build. Since it was my first project, I felt having more power than I needed would be better than needing more power. This pump can go 6 ft vertical, but I could probably have gotten away with 3 ft.
The 4 ft lamp I used seems to be plenty good for this bed. I grabbed a 2 ft lamp as well for the bottom section. Most fish don't require light, but having one is nice if you ever need to inspect anything in the tank. It also gives you the option of making floating grow beds or growing your own duckweed directly in the tank.
The reflector on the lamps is a fraction of an inch wider than the space between the shelving posts. The doesn't matter for the 2 ft lamp, but putting the tiniest bend in the 4 ft reflector will make it fit just fine.
Step 4: Fill and Cycle
Now for the last step before we add the organics.
For my grow medium, I am using red lava rock. It's significantly less expensive than hydroton, but it is a lot more rough. It also comes with a lot of dust that can make your water really muddy. I would recommend rinsing your rocks before putting them in.
After we've got all the pieces assembled, we still need to get the system cycled. Cycling is allowing the bacteria to show up that will turn the fish waste into plant food. I used fishless cycling with some store bought ammonia. Essentially, I added some pure ammonia to the system each day until it started turning into nitrates. More importantly, this period provided and stress test to my plumbing. I found multiple errors with my system that I was able to adjust before I had plants and fish.
Step 5: Plant and Automate
Once we know the mechanics of the system work, and we've got nitrates in our system, we can set it to run without us.
I used a simple timer for the lights because their pattern is a really simple on/off. For the pump, I found a programmable timer that I could set multiple intervals on down to the minute of the day. It takes about 7 minutes for the bed to fill and 3 to empty. With this timer, I was able to schedule fills and make sure the pump was off while it emptied.
If you get your plants from a traditional nursery, you'll have to rise the roots to get as much soil out as you can. Depending on the roots, this can be easy, or it can be really tedious. Either way, expect a little bit of die back after you get them planted.
Step 6: Harvest
I would recommend starting with plants that are less demanding, like spices or leafy vegetables. Similarly, I started with cheap goldfish in my tank. They're nice and hardy. If you make some mistakes, you'll have some time to get your levels back in line before everything dies.