I’ve been tinkering with something for a couple of months now and it may be of interest to some here. It’s called aquaponics and is a combination of aquaculture (raising fish) and hydroponics (raising plants without soil). The key is the nitrification cycle: The fish give off waste (mainly ammonia), bacteria in the plant growing media break down those wastes into nitrites and then nitrates, the plants absorb the nitrates and other elements to grow, and the now clean water flows back to the fish. It can be a delicate thing to balance but once it’s running it can run very smoothly with little input.
I decided to set up a system in my shop which presented me with a few challenges. First off, I only heat it to 45-50F unless I’m out there working and that’s kind of low for fish or plant growth, or even survival. Second, there’s not much light in there so I have it in front of a mostly shaded window and am running supplemental lighting. The heat issue will change once warm weather comes back and I may then try to move the grow beds (or the whole system) outside, into the sun.
This is what I started with, a used IBC tote:
I cut the top 12” off, inverted it, and set it back on the remaining part. The top part is the grow bed (GB) and the lower part is the fish tank (FT). Here are a couple of more recent photos:
As you can see, I also added an old bathtub as a second grow bed. One of the governing ratios to maintain is that the GB volume should equal the FT volume if you want to stock fish to densities of 3-5 fish per gallon. I have 150-200 gallons of FT volume and about half that in GB volume.
The IBC GB is filled with lava pebbles and there is a standpipe in the middle to set the max water level (1-1.5” below the top of the media). A fountain pump in the fish tank fills the GB through the PVC pipe around the perimeter and it runs on a timer: 15 minutes on, 45 minutes off. The tub GB is filled with pea gravel and has a separate pump constantly flooding it to the correct level. The drain draws water off the bottom to promote good flow and routes back to the FT.
I am running two 500 watt heaters in the fish tank and currently have them set at 80F. There is a 4 outlet air pump with air stones keeping the FT water oxygenated. I also made a 12 volt back-up system (deep cycle battery, bilge pump, relay control) to kick on if the power goes out.
I have some plants going that I pulled out of the fall garden and have also planted some seeds directly into the GB media. On 1/10/13 I added the protein – 50 blue tilapia fingerlings. They are doing well and getting chubby. If thing go right they’ll be on my plate in about 9 months. Yellow perch or hybrid bluegill were my second choice but the tilapia won out for various reasons. I really only have enough room for about 25-30 fish so can stand to loose a few or I’ll chow down on some smaller ones when they’re ready. Here are the tilapia getting ready for their new home:
So far, it’s been a fun project. There is so much to learn about the fish, the plants, the nitrification cycle and making it all work together.