Smart Aquaponics Control System – An Internet of Things project
In my last post, I’ve said that I want a project that helps me control an aquaponics system. These are both very vague goals, and I need to narrow them down, and then I need to figure out how to do them. It seems a bit silly to use Project Management Processes and Product-Oriented Processes to define and control my project when I am simultaneously the management, employee, and customer. However, it is still useful for me to define the project in these terms in order to create a timeline, benchmarks, and goal.
To start this I’ll first define what sort of aquaponics system I want to control, and speak about the constraints I must follow. As an aside, I’ve heard it said in many different contexts that any problem is easily solved if you do not have to worry about constraints. Even sending humans to Mars becomes much easier if you don’t have to worry about them arriving alive – or ever departing again! A round trip to Mars with living humans is considered a “constraint”.
What is an aquaponics system?
Aquaculture is the raising of fish (or other aquatic animals) for food. Such a system requires food and clean water, and the wastes from the system must be filtered out of it and disposed of, or else the system will become deadly to its animals. Hydroponics is the growing of plants in water for food. This sort of system requires that the water be fertilized and filtered, and watched for build-ups of waste and metals, or else the plants will die.
Aquaponics is a combination of these two methods of growing food, such that the wastes of the aquatic animals are used as fertilizer for the plants, and the plants clean the water for the animals. There is also a layer of nitrification bacteria in the system that break down ammonia and nitrates into nutrients for the plants.
In a perfect aquaponics system, you put fish food into the system, and you get meat and plants out of the system. Having said that, no aquaponics system is perfect, and a certain amount of tweaking the system is necessary.
To the right is a good example of a very simple aquaponics system. This system uses a pump to move water from the fish tank to a filter tank. The filter tank is filled with media that houses nitrification bacteria. This describes nothing more than a standard aquarium, and such a setup can be very stable, needing little in the way of maintenance if the ratio of fish to bacteria stays stable, and if distilled water is added to the system to compensate for evaporation losses.
The addition of plants to such a system runs into an immediate problem. Some plants cannot survive with having their roots constantly submerged in water. They need to be able to have access to air. One way of doing this is to periodically drain the upper media tank several times a day. A good mechanical way of doing this is to use a self-starting siphon called a “Bell Siphon“.
In short, a Bell Siphon will start to siphon water from the upper tank when the water reaches a certain depth. It will stop pulling water out of the upper tank when the water level drops below the rim of the Bell dome, which is typically near the bottom of the container. If the container is sloped toward the siphon, then most of the container will be completely drained.
This simple siphon works fine for a small aquaponics system. Something like the one shown to the right. This is a 150 gallon tank with an 80 gallon media bed. At the time of this photo, I was experimenting with Bell siphons, and had not added media to this project.
But what happens when you have multiple fish tanks? What happens when you have multiple media beds for your plants? What do you do when you want to add other aquatic animals besides just fish? Like freshwater prawns or mussels?
As I continued to play with aquaponics systems, the next thing I knew I had over a thousand gallons of fish tanks, and I was trying to find ways to circulate their water, and also to be able to drain them when I needed to clean them. This is what I came up with.
This system doesn’t even count the plant grow beds. It also uses a common sump tank as a shortcut. It did have the advantage of allowing me to drain a tank if I needed to do so, but with the disadvantage of requiring me to re-route the circulation if I wanted to cut off a center tank.
I actually built this system, and documented it on my permaculture website, with a video of it in action. You can see this here.
And I ran into a problem. Okay, one of the problems I had is that I had to move, and was required to disassemble the system.
But what I consider to be the bigger problem is how the system worked together. If I added grow beds to the system, I had to be concerned with my sump “bottoming out”.
The grow beds that I want to use are two feet wide, four feet long, and 14 inches deep, with 12 inches of media. This translates into 60 gallons of media and water together, or about 25 gallons of water per grow bed. This means I can have no more than 7 grow beds before my sump goes bone dry. Or less than 6 grow beds if I want to keep my sump pump underwater.
This also doesn’t account for water diverted to strawberry towers, lost in evaporation, or used in other ways. I would like the ability to use 10 grow beds or more, and use the sump itself (with a screen around the pump) for growing catfish. So a certain amount of water must remain in it.
This is what I came up with… multiple tanks, multiple grow beds. Of course, the sump would have to be larger, just in case all the Bell siphons achieved synchronicity and allowed all the grow beds to fill up at once. There would have to be enough water for everything.
Each of those red handles represents a valve that can be turned off or on by hand, and that I would be expected to fiddle with to get the right rate of flow for the system. And while this is quite acceptable with a smaller system, it becomes a problem larger systems.
Luckily valves and pumps can be controlled through electronics. I wanted an inexpensive method that I could create, and that I could offer to the Maker and Aquaponics community. I’ll talk about that next as I more formally describe the scope of this project.