Transcript of my interview with Aquaponics expert, Mihail Mateev.

-First of all, could you describe aquaponics? What it is and how it works.

-A  Aquaponics is a closed ecosystem of edible fish and plants.

It is a combination of industrial breeding of fish, which is called aquaculture and soilless growing of plants, which is called hydroponics (where the inorganic nutrients are dissolved into the water). The combination of these two terms makes aquaponics.

In aquaponics we feed the fish, they grow and they produce ammonia, which resides into the water. Then bacteria convert ammonia to nitrites and nitrates, which are consumed by plants.

So the benefits are mutual: plants receive nutrients at constant rate and fish have their water cleaned by poisonous in descending degree ammonia, nitrites and nitrates.

The water is moved by a water pump from the fish tank to the plant tank and then it is moved back to fish tank under the force of gravity.

What are the advantages of aquaponics compared to usual soil agriculture and classical aquaculture and hydroponics?

A:  Regular agriculture is done in extensive way – when more production is needed, more land is sowed. Water is not contained within root zone of the plants, but it is mainly relied on the natural rain during the warm seasons to water the crops. When there is less rain we face a disaster. On the other hand, when we need more production per acre, we put different fertilizers, which are transported by water. Unfortunately the effect of the fertilizers is limited for the time when there is first, rain after putting fertilizers into the ground, and second, the period of which the fertilized water stays in the root zone of the plants. This period is usually short, and therefore fertilizers need to be in higher concentration, so effect can be achieved. After this this rich of fertilizers water have passed the root zone, it naturally goes to the lower levels until it reaches sub terrainian water, and this way the fertilizers contaminate sub terrainian water, which is used as potable water from humans and animals.

While soil agriculture is feeding the world population successfully, it does it in a quite ineffective way, and there are different prospects that the food in the future would become more expensive as the demand for food will increase. These prospects are based on regular agriculture. As we saw, it is ineffective in water usage, in fertilizer usage and in addition, it contaminates the potable underground water.

Aquaculture – the industrial breeding of fish – is none the less inefficient as the water is discarded on a regular basis, because it is contaminated by fish byproducts (which is a usual practice even for ornament fish aquarists). So ammonia rich water (and may be even water contained antibiotics and other medicines) is released into artificial ponds, or rivers and water channels where it contaminates natural environment if it is processed through an expensive treatment plant.

In hydroponics we have a water solution of several elements – nitrogen, phosphorus, and potassium (also called NPK). The problem is that within 4 (four) weeks the solution is impossible to be rebalanced as in the initial state (although some large hydroponics installations operators report they make this period longer), finally the water, full of unbalanced minerals, is discarded in a way similar to the one, discussed for aquaculture.

Aquaponics, on the other hand, is a closed system. The water is constantly moved from fish tank to plant tank and back to fish tank. It does not rely on special chemicals, it relies on fish food and some water to keep the loses of evaporation and plant consumption, but as a general rule water is never discarded. Reported efficiency in regards to the water is less that 10% usage in aquaponics compared to regular agriculture for the same amount of production. Aquaponics also is area-wise, because the plants may be planted more densely, because they do not compete for nutrients, as nutrient-rich water is always available. Also, aquaponics is possible to be run in urban environment, and to use what-ever space is available in horizontal and  vertical direction, because it is soilless and also because plant containers are able to be stacked in stories. There are video-clips of aquaponics done in old buildings, repurposed for aquaponics.

And the last advantage, but not the least, is the fact that with aquaponics you can have fresh plants, which are locally grown. This means they would have ripen on the stem and not in the ships or trucks during transportation. This would mean they are healthier and tastier.

-What types of aquatic flora and fauna do you envision growing in a self-contained aquatic environment?

-A  Generally aquaponics is a fresh-water environment, which means fresh water fauna is breed- mostly different kind of fish (mostly different kinds of carp, but also trout, goldfish, etc), and also shrimps and crawfish/crayfish, and may be even some mussels.

As for the flora – most of the land plants can be grown, keeping respect to different species requirements – for example leafy vegetables prefer more water, while other prefer less water – tomato, potato, strawberries, etc. There are several different types of plant containers to meet these different demands.

-What type of equipment is required in order to sustain such an environment?

-A  The absolute minimum for aquaponics system is to have a container for the fish, a container for the plants, some pipes and a water pump to move the water from fish tank to plant tank. And constant access to energy for the pump- and emergency power source in case the main power source fails for any reason.

Optional equipment is air pump, illumination, timer, heater, and chiller, different kinds of monitoring and automation equipment.

-Would the aquatic medium be salt water or fresh water, or possible both?

-A  As a rule fresh water is used in aquaponics. The plants that are usually grown, are land plants, and they do not tolerate high levels of salts, which present in salt water. But salt water must not be discarded and may be some seaweeds can be grown in salt water in a closed recirculating system.

There are only a few edible fresh-water aquatic plants, which is possible to be used as plants in aqupoanics, but they are not of such interest among aquaponicists.

-What are your thoughts on the effects of reduced gravity on aquatic plants and animals?

-A  Unfortunately the humanity does not have any reduced gravity prolonged experiments with plants or animals, apart from ones grown at International Space Station, but there the extreme is there is no effective gravity.

So my suggestions are pure speculations – the animals would adapt quickly in reduced gravity, the plants might or might not have increased transpiration, which was detected in microgravity.

– How much space would such an installation require in order to provide food for the Mars settlers?

-A Here the opinion differs.

Mars One foundation says in very short statement that 50 square meters would be enought to provide food for four settlers.

“In total there will be about 50 m2 available for plant growth…. There will be sufficient plant production capacity to feed about three crews of four.” – See more at: (accessed 20141230)

MIT researchers, in their famous report on Mars One feasibility ( – accessed on 20141230), claim no less of 200 square meters per crew (four people) plant area is needed for five (lettuce, peanut, soybean, sweet potato, and wheat) out of nine crops (because diversity in food is needed): dry bean, lettuce, peanut, rice, soybean, sweet potato, tomato, white potato, and wheat. But as mentioned before, plant containers may be stacked.

It remains unclear if Mars One’s 50 sq. m. are the floor print with 4 stories, or the total plant area.

-Can the plants and animals be shipped to Mars in egg form?

-A Plants can be carried in form of seeds, fish can be transported in form of fry and sperm and fertilized on arrival (such deep freezing is done with the gametes of other animals – horses for example. The same approach is used with humans, too). Or it can be transported with living fish.

-Do you envision this as a food supplement source or a mainstay source?

-A My vision of aquaponcis is as a operational mainstay source of food, which means food will be provided locally by other animals – different kinds of birds, animals, insects, etc. The main thing is food independence, therefore self-sustainability of the settlement. And aquaponics might have a big share in this.

-Discuss the advantages of aquaponics over regular gardening or hydroponics in a Mars settlement.

-A The main advantage of aquaponics over regular gardening and hydroponics in a Mars settlement is its simplicity. For hydroponics one has to produce special solution of carefully selected chemicals, and the tests with Martian analogue regolith soil growing of tomatoes showed that heavy metals are available in the soil and those heavy metals are collected in the fruits of the tomato plant, making them poisonous and harmful for people (, accessed 20141230)

-You recently gave a presentation on this subject. Could you give us the highlights of that talk?

-A Yes, I gave a presentation on aquaponics on this matter. The most important  points I spoke on were what is aquaponics, advantages of aquaponics as food producing method, which are already covered in this interview and finally I demonstrated an aquaponics setup, made out of shelf off containers, pipes, and some aquarium equipment.

-You have referred to an aquaponics apparatus you have developed. Could you describe it and its purpose?

-A This aquaponics setup contains of 30 L fish tank, 10 L plant tank, a small aquarium pump, some pipes and other optional equipment – lighting, heater, air pump, etc.

The purpose was to prove aquaponics is possible to be done with readily available items, and this way to inspire teenagers to create their own aquaponical systems and gain knowledge and expertise along the way while they do it. So one day they be able to be the specialists of food production in Mars settlements.

-Any other topics you would like to discuss?


Thank you for taking the time for this interview.

A-You are welcome and thank you


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