Winter has proved to be an interesting time and predictably the major issue has been with temperatures. The problem with Tilapia, being a low-value fish, is that one cannot afford to invest huge amounts in heating during Winter, so innovative means have to be found to keep them happy. My situation is slightly different, in that my Aquaponic system is actually a hatchery, so I don’t mind spending a little bit more to keep my top brood fish comfortable for the hard work (?) ahead.
I have also been busy researching alternative methods of heating in order to come up with some workable ideas for my clients for next Winter. I have concentrated my efforts of two main topics.
While I doubt that solar can produce enough cheap heat for a large Aquaponic system, it certainly has merit as a supplementary source of heat. It’s major drawback is that it is only effective during cloudless, daylight hours. My research has focused on making existing solar heating solutions more efficient. I have recently come across a locally-designed “solar tracking” device (still in the developmental stage) that tracks the sun in order to get that much more out of the system. It basically follows the sun like a flower, but obviously depends on the sun actually being visible. I, on the other hand, am working on a computerised system that instead of tracking the sun based on where it is visble, aims the solar array at where the sun “should be”. It works on an algorithm based on the date, time, longitude and latitude. Given these 4 inputs, my algorithm plots exactly where the sun is at any given time and two small DC motors will set the horizontal and vertical pitch of the array to aim it optimally at the sun, even if it isn’t actually visible at that time.
Another really interesting means of heating the water could be the composting process. I recently built a trial composting bin and the temperatures that I am getting within the pile are very impressive.
I have found that the best heat is obtained in the first two weeks of composting and also that the more the material is aerated, the faster and better the composting process proceeds and also the higher the temperatures become. What I’d like to do now, is to build a bigger composting bin, say 6m x 1m. I then want to run black 40mm irrigation pipe through the middle of the bin and pump water through this before returning it to the ponds. Like solar, I am sure that this couldn’t provide all the heat required, but it would certainly work as a supplementary source of heating.
Another method that I’ve used this Winter at my home AP system and one of the commercial sites is to reduce the volume of water to be heated. This cuts down on the heating bill and one can also use a smaller heat pump to achieve the same temperature. I have moved all of my fish to one pond and removed the standpipe from the other. This has reduced the water in this pond by 1/2. I am also running my sump very low.
On the subject of water, we had very good rains last week and my storage tanks and “koi” pond are all filling up nicely. The koi pond I will be using to grow out some Tilapia for our restuarant this Summer.
In moving the fish, I has an opportunity to have a closer look at how they are doing. The males are “huge” and are now well over 1kg and the females also look in great condition. I’ll keep them together now and then seperate them in September for a few weeks before the breeding season to get them “in the mood.”
To keep the wolf from the door I have been hard at work building a greenhouse tunnel for a trial Aquaponic system just outside Uitenhage (near Port Elizabeth). It’s an extended tunnel of 37m x 9.5m and we have been working in the most horrific conditions with gale force winds, dust, rain and freezing temperatures. In the 11 days spent on site, I had one morning where the wind didn’t blow. Obviously the design and build of this tunnel has had to take into account the adverse weather conditions and the gable ends have been re-inforced with shade cloth and the whole tunnel has been covered with hail netting. Here are two images of the tunnel during construction.
Enough for now.