This is a type of farming, consists of two main parts: aquaculture (cultivating aquatic animals) and hydroponics (cultivating plants in water). In order for this system to function, bacteria need to be added to the system as well. The whole system is divided in numerous compartments, that include systems for effective removal of waste, filtration system, neutralizing acidic water, maintaining water oxygenation etc.
They are being held in rearing tanks, which are used for raising as well as feeding the aquatic animals. Since they are the main role character in this closed ecosystem, keeping them happy is very important. In order to reach that, we need to pick a type of an aquatic organism, that tolerates crowding. The animals, that are most commonly used are fish (mostly Tilapia), crayfish and prawns. Animals grown in this way, are usually used as (human or fish) food, when they reach their optimal size.
When feeding aquatic organisms in a closed ecosystem, there is always a lot of food, that was not eaten. If left in the tank, its accumulation can lead to development of diseases, which will affect the overall health of an ecosystem. On the other hand, there are also high concentrations of excretions (poop) and ammonia (comes from breathing) present in the tank. Excretions will sink to the bottom of the tank (usually into a special compartment) and ammonia will dissolve in water. Since we speak of a closed aquaculture system, there can only be a specific amount of toxic substances and nutrients, before they start affecting the health of organisms.
So, where can we put all of these substances in order to keep the aquatic organisms happy and healthy? Yes, you guessed right – we give it to plants, that just can’t wait to get their roots around them!
So, we have too many nutrients in the ponds with our aquatic animals, and we really need to do something about the alarming high concentrations of nutrients, or else, everything will die! Well, there is nothing easier than planting a few plants to do the trick! And while we are on it, why not plant something we can actually use, like vegetables? As it turns out, there are many plants, that just love the feeling of having their roots sumberged in the nutrient-rich water. Since the concentrations of nutrients are so high, they also don’t have to really fight for them, they just have their mouths (or canals in the roots) opened and the nutrients come to them! So, voila! The problem is solved!
Of course, not all vegetable species require the same amount of nutrients, and it is also true, that younger plants need less than the mature plants. Thankfully, we can very easily (electronically) regulate the amount of dissolved nutrients in this closed ecosystem. If the plants require less nutrients, we can either have lower number of mature or higher number of smaller-sized individuals in the pond, and vice versa. Another option is, to regulate the number of filters and other surfaces, suitable for growing of bacterial colonies.
But… bacteria are bad! You don’t know what you’re saying!
Yes, SOME bacteria are bad and many of them play very important roles in nature as well as in this closed ecoystem of ours. Here, we do our best to grow two types of bacteria: one, that converts ammonium to nitrites (Nitrosomonas) and one, that converts the nitrites into nitrates (Nitrobacter). This step is very, since the transformed elements are safely stored (and unable to bind on oxygen), but still available for the plants to use. Bacteria also play a big role in reducing the acidity of the water.
Do you remember, when I wrote about the food, that sinks into a special compartment at the bottom of the tank? Well, this compartment needs to be cleaned very often in order to prevent spreading of the disease. But there is another thing you can do – add worms. They role is actually pretty awesome, since they have the ability to turn the solid organic matter into liquid and therefore make it available for bacteria and plants.
Operation of these systems
There are five main inputs into the system water, oxygen, light, food for the aquatic animals and electricity (heating system, pumps, filters etc.). I dont have a lot to add with oxygen and light, since we all know that this is something, many (not all) living organisms need. However, i woluld like to talk about other three topics, since they usually raise more concerns. There is a lot of talk and concerns about the unsustainability of food used to feed aquatic animals (this is also true for sea fish farms). Currently, the food is mostly made out of fish species that we refer to non-valuable species (do not sell under high prices, injured, caught as bycatch, etc.). Scientists are doing a lot of research in order to solve this problem and so far they have already found many alternatives, such as: duckweed, prepared kitchen scraps, farmed soldier fly larvae etc.
When speaking about the problems of water and electricity, I need to calm you down. This is one of the farming methods, that uses very little water. The water in the system is circulating the whole time, and it only needs to be added in order to cover losses due to evaporation from the water surface, removal of waste as well as absorption and transpiration of plants. When comparing the amount of used water to produce the same amout of vegetables in a convenctional way, we found that 90- 95% less water was used. In order to save the electricity, we should make our farm as highly efficient as possible. Another thing, we need to consider is, (if you are lucky and live in the country, where this is possible) to choose the providers, that care about the environment. By this i am referring to the ones that get their electricity from sustainable sources (wind, solar etc;) and not from providers, where fossil fuels are burned.
I strongly disagree with the fact that hydropower is produced in a sustainable way, well, at least not all of it. The effects on the environment, when building powerplants on the rivers are just to big to pretend, that we dont see them, but the situation is a bit differenet for the powerplants built on the sea. You can read more about my thinking here:
The best part is, that the vegetables and aquatic animals that we produce are not treated with therapeutants and/or pesticides. In these closed ecosystems, treatement and protection from diseases and pests are done with physical barriers and the interactions that naturally occur between the organisms. Occasionally, some substances for neutralising the acidity of water or some nutients and minerals can be added, in order to boost the overall health.
As you see, many calculations, monitoring and measurements need to be done and mixed with deep knowledge in order to have a functioning closed ecosystem. In time and after more research in ecology and simmilar sciences, management of this complex, yet simple ecosystem could become easier, but for now, we still have a long way to go.
Do you also think, it is completely crazy, that we have managed to come so far and and connect all these variants into a well- functioning closed ecosystem? For me, this really is something breath taking, eventhough we still have a long way to go.