We did not create blog-posting updates for all the trial and error we experienced over that last month or so in trying to get this aquaponic system going. We have had about three failures and learning experiences about getting the mechanics working. Our goal was to pump the water out of the tank that has fish in it, run it through the mechanical/biological filter seen in the bucket at left, run the water through the two hydroponic trays that contain the plants, and finally drop the water back into the tank. The nutrients from the fish waste are supposed to provide for the plants once they are processed through bacteria in the biological filter.
The challenging part in getting this system going was design of our mechanical/biological filter. We did a little research and found out we could build our own filter out of a 5 gallon bucket, some hose and fittings, and filter media like pumice, sand, gravel, charcoal, or commercially obtained sheets of pond-filter-media. Our main problem was getting the outflow of the filter of sufficient volume to accommodate the volume of water that was entering the filter. We had to balance the gallons per hour of the two pumps we tried as well as the total diameter of the outflows which are different sized polytubes as seen on the far left of the photo. To summarize, we had to reduce our pump size from 550 gallons per hour to 160 gallons per hour and we had to increase our outflow from five 1/4″ polytubes to an additional 3/4″ polytube. The 3/4″ tube meant that, for now, we had to lose the topmost planting hole in the hydroponic tray. The fact that we lost almost 50 fish a couple of weeks ago will also compromise the capacity of this system. But for right now we have about 10 gold fish and 2 bottom feeders so hopefully this will be sufficient to at least ascertain the potential of this system for future fine-tuning. We did not populate our hydroponic trays to capacity to account for the potential deficit of nutrients from a smaller fish population and just plugged some holes that we can use in the future. It is likely that some of these plants will not survive the transition and we will have even less plants surviving in the system by the time we get more fish. We are hopeful to receive another donation of blue gill fish from the NM Department of Fish and Game sometime in August.
To elaborate on the design of our filter system, we used the 5-gallon bucket pictured above. We bought three bulkheads and drilled holes in the bucket, one on the bottom (inflow from water tank) and two on the top (output to hydroponic trays). We ended up using 1/2″ inner diameter polytube for the inflow and 3/4″ inner diameter polytube for the outflow. We got these materials from the local hardware store in the drip irrigation section. We put in five 1/4″ polytubes from the 3/4″ line using drip irrigation fittings. We had to finally just ‘T’ in to the 3/4″ line and put it in one of our holes that was intended for a plant (see below). Our biggest problem in all this was accommodating the outflow from the filter. I didn’t want to drill all kinds of holes in the tray lid, so that limited my options. I always try to remember the old Permaculture saying as I go along: “The least change for the greatest benefit.”
We used internet-bought pond media and made a couple of layers on the bottom of the bucket. This media is like a swamp-cooler filter or a heater filter and something like that could also be used. We bought a couple of sheets of coarse and medium density and figured we would use it over and over for different applications over the years. Given the semi-modular character of the system, we can switch out bucket filters of different materials and do water quality tests with the in- and out-flows to find out about the best filter media. We cut the media into circles with a serrated knife and packed it into the bottom of the bucket. Then we covered the three media layers in about a two inch layer of pumice and covered that with about an inch of pea gravel. Eventually we might incorporate our biochar as a layer and/or a layer of sand. We may even get in another bucket to make a dual-filtration kind of system. But our priority was to get this up-and-running so we could try it out and tweak it. Another Permaculture saying comes to mind: “Make as many mistakes as you can, as fast as possible.”
The two pictures above show how the plants are suspended from the lid of the hydroponic tray so that their roots can penetrate into the flowing water underneath. The tomato plant on top was kept alive by floating on a raft in our water tank and is now held up by a rubber grommet that was purchased for this purpose online. We now buy these things locally at EarthGoods. The little fiberglass-like plug in the photo above contains a watermelon plant. The fiberglass plug has a hole in it where we deposited the seed and watered it as if it were a seedling start. We had to be sure to keep the plug almost saturated in water to keep the growth of the roots going. The roots have to be 2-3″ long to reach the water and we are not sure if all of them are going to make it. Stay posted for future developments; this is one of the most innovative projects we are involved in and learning about right now…