Without further delay, I present to you our (roughly) 200 gallon aquaponics system, built from re-purposed wood, a cheap pond kit, some PVC, and lava rocks.
Step 1: Tearing Down the Old Raised Beds and Getting the Base Built
What really prompted this project was the fact I was getting very tired of the fire ants getting into my raised beds. After losing much of my crops to ants, I decided I was going to grow in water via hydroponics. Then, I was able to convince my wife to let me put a fish tank on the deck for another aquaponics build - so it was on ;)
Thanks to the help of my son, all of the 6" screws were taken out of these timbers, we cut them to size and ultimately built a smaller version for the tank and used some of the pieces for legs and supports on the grow bed. It is worth noting that we were able to reuse most of the screws that came out of the timbers as well so I did not have to buy any.
The size of my grow bed and the size of my tank were based on mathematical calculations made by me based on the amount of pond liner I had available to me. I bought the kit (see picture) on Craigslist for $25 - it was still brand new in the box. The liner was 8x10 so I had to figure on how much I could use of this. I elected to build a tank that was 2x7 x18" deep and grow bed was 1x7 x1' deep for optimal root space. Of course, if you are using a different size liner, just keep in mind that your depth will take off length and width from ALL sides (if you go 1' deep, you need to take off 2' from length and width, which works out to 1' all the way around)
Step 2: It's Coming Together Now
We built the tank entirely from landscapes timbers for extra rigidity as they are less prone to bowing in the middle. To strengthen them, we did add an additional screw in the middle of the long runs so that each timber is securely fastened to the one below it to remove the potential of bowing on the long side.
The grow bed was pretty straightforward. I measured the inside diameter and calculated that I would need 3 deck boards for the width (note that the deck boards were all leftover from when we built the deck a couple of years ago). I then used landscape timbers for the legs and supports that the bottom boards would sit on. I also used deck boards for the sides with the exception of the two ends. I ran out of enough deck boards but had a few scrap 2x12 pieces that I was able to cut a few inches off and use them (note: save all wood pieces over 1' if you have room to store them - you never know when they will come in handy).
Note that the measurements have to be pretty precise on all this because once you put a couple hundred pounds of rocks and almost 500 pounds of water in this bed, it will not be very happy if it uneven and out of level. That being said, there is a little room for forgiveness - just not much :)
Step 3: Getting It to Hold Water
The next step is laying down the liner. Remember that I cut the liner in a way to get both the bed and tank out of one liner. Now, we put them in to our built structures. The MOST IMPORTANT thing here is to put them in with a little slack. As the water is put into the system, the liner will fill all the small cracks, etc and without some play in the liner, you run the very real possibility of ripping it as the weight of the water pushes on it.
I used the felt paper nails you buy for roofing to hold the liner in place. Note that I only put them on the very top of the liner so there is no risk of leakage around them. There may be other things that would work better but these worked awesome and I just so happened to have half a box left over from when I built my shed so it is another thing that cost me no money.
You will notice that I have already added lava rock to my grow bed. This was primarily so I could keep the liner in place while I tested my Bell Siphon.
What is a Bell Siphon you ask? In the system, water is constantly being pumped into the grow bed. As the bed fills up, we use this siphon to quickly release the water back out of the bed. This allows for roots to get water and then removes the water off of them, creating a constant cycle of nutrients and water to the roots.
How to make the Bell Siphon. My apologies, I did not take pictures of this, but I feel that you can follow me pretty easily (and you can google images if you don't). Most Bell Siphons have a tube running from the top to the bottom - mine does not. If you have ever seen one or google image it, you will know what I mean. I did not use an air suction tube. Instead, this is how I make mine:
1' PVC is your drain tube (see pic) and needs to be mounted securely to your bed and go through it to your fish tank. Your 1" PVC should be 1" below the lowest point of your liner. (actually about a ½" but I give the extra half to be on the safe side
A 2" PVC pip with a cap should be cut to where it stands (with the cap) approximately 1" higher than the highest point of your 1" PVC. On the bottom of this, you will need to cut small slits so that water can enter into it but rocks, etc cannot. Your HIGHEST slit should be no more than 2½-3" as whatever your highest slit is in this pipe is what your constant water height will be in your bed (some water will always stay in the grow bed. The siphon will suck air when the water gets to the first air slit and it will break the siphon. Put the 2"pipe over the 1" trying to center it as best as you can.
Cut a 4"PVC pipe to 1-2" above the tallest point on the 2" pipe and drill holes all over the place. The only purpose of this pipe is to let water through but create an additional block against the rocks.
(I know, I spent more time on the siphon, but it is a VERY important part of the system)
Step 4: Putting Together the Rest of the Plumbing
Now, what you can't see in these photos is that there is a 1" PVC pipe running from my pump to the opposite side of the grow bed. It is hidden under the bed. I used a T-splitter to create two water streams. One goes to the bed and the other is going long-wyas doen the strawberry towers and will be set to a trickle.
The 4" pipe below is being used as a return pipe for the water from the strawberry towers. Where the towers meat the pipe, I have also created another growing spot so the entire pipe is filled with rock.
You will need PVC cement to attach/glue the connections. Make sure you get it on there good so there are no leaks.
Step 5: Done - FAQ
Upon completion, you will need to "cycle" your system before putting fish and/or plants in.
There are many ways to do this, but the most accepted way is to go ahead and put in plants and use seaweed extract (in accordance with label directions) to build up bacteria needed for the system.
Other ways to cycle system include urinating in it and waiting a week or you could throw everything together and just take out the few fish that will die in the process.
I put together a few things you may find interesting or that may come up as questions although I do welcome any questions and feedback.
1. How does the system work (biologically)?
Fish waste is pumped up through the system into the grow bed where bacteria convert it to nitrates for the plants. The plants then use those to grow, effectively cleaning the water or filtering the water for the fish. It is a completely closed loop system.
2. Do I need to monitor the fish/water?
As a typical rule, I would say "yes, of course". That being said, once your system has cycled and is stable, you should be able to let it be with the exception of feeding the fish.
3 How many fish do you need?
Most agree that about 1 10-12" fish per gallon of grow bed. You can calculate your rough grow bed volume with the formula - length * width * depth * 7.5 as there is roughly 7½ gallons per cubic foot of area.
4. Why did I grow goldfish instead of edibles like trout or tilapia?
Because I live on the MS Coast where I can get plenty of fresh fish much larger than what I can grow. Also, the temperature variances will allow me to grow goldfish through heat and cool lessening the chance of loss of fish in extreme heat or the occasional freeze in winter. Plus, my wife thinks they are pretty.
5. How did I make strawberry towers?
cut about halfway through the 4" PVC and use a heat gun to soften the plastic then pushed in on the middle with a hammer (softly) to form it. Use a filer/respirator though as PVC can release harmful chemicals when heated to extremes and you don't want to breathe it in.