Six things you shouldn't ignore, as they are vital to Aquaponics

1. Fish stocking density

Each fish requires a minimum volume of clean, oxigenated water for healthy production. The size of fish production tanks would inherently limit the quantity of fish that can be stock within. The fish stocking density is the density in which fish can be stocked in each tank without overcrowding, and other leading factors that all lead to fish mortality.

We operate 4 fish production tanks in Freeport. Relatively small each with approximately 375 us. gal each. We stock anywhere between 80 (mature fish)-100 (fingerlings) fish in each tank.

2. Plant to fish ratios

Because of the symbiotic relationship of the aquatic animals and plants in Aquaponics the ratio of fish to plants become very important. The fish so because they are required to provide nutrients for the plants. Each plant and season of crops would require a certain amount of nutrients and this is controlled in part by the quantity of fish and by some extent the quality of fish feed, which directly determines the quality and health of fish and organic nutrients available to the plants. The plants so because they are required to absorb all the nutrients and clear the water of toxicities before it is returned to the fish, there should be sufficient plants in order to clean up the water to suitable levels for good fish health.


Our plant to fish ratio is approximately 1:1 (1272:1125 us gal.)

3. Filtration

To clean up the water for the fish, a filter is used. The filter is responsible for removing for the fish toxic ammonia, nitrites and nitrates both settleable and floating solids that would typically be produced in the fish component and otherwise left in suspension or form a colloid. This is typically done biologically and  mechanically. The mechanical filter is where settleable solids and floating solids are removed. 

Ammonia, produced by the fish, is toxic to fish if allowed to accumulate in aquaculture systems. Ammonia is removed by oxygenation of the water, the process converts toxic ammonia usually products by the fish to nitrates, and nitrates which the plant utilizes. A process called nitrification. In aquaponics there may exist non-turbulent areas where denitrification could occur. Denitrification is performed primarily by heterotrophic bacteria, under anoxic conditions, which is comparable to anaerobic conditions except for the presence of nitrate and/or nitrite. During denitrification, nitrate is reduced to nitrite and then to nitrous oxide, which is finally reduced to nitrogen gas.

In Aquaponics the plant component forms part of the filtration system. This is the bio-filter. The bio-filter is responsible for cleaning up the water further, absorbing the nitrites and nitrates that if left would be toxic to the fish. While the plants act as a natural biofilter, absorbing nitrites and nitrates from the water and using them for fostering growth. In this way, the plants filter out all the harmful chemicals, all the fish waste from the water and render it safe for the fish. 


In Freeport our filtration system consists of four units: The Clarifier, the Net Tank, Degassing Tank and the Plant Component.

The Clarifier is a cone shaped VESSEL with baffles that slows down the flow of water THROUGH it allowing solids to settle in the process. Solids that settle are removed manually from the system.

The Net Tank uses nets to trap solids in suspension, floating THROUGH as the water flows.

The Degassing tank pumps air into the system which is responsible for, together with teh system microbes the oxidation of ammonia to Nitrites and nitrates, and Nitrogen gas useful to the plants growth. This process is called nitrification. The plants absorb the Nitrites and nitrates before the water is returned to the fish. 

4. Wholesome, nutritious fish feed

In our Freeport operation this remains a challenge as we have found no source of nutritious feed locally and have to rely on imports and the availability of more nutritious and wholesome imported feed. This is a pain point and a topic for another discussion.

5. Biological Surface Area

Microbes hang our on the surface area of the system exposed the the system water, this is called the biological surface area, and these microbes help to keep the system healthy.

To start, biological surface area (BSA) is the amount of surface area inside your system that on which microbes can live. BSA is very important in aquaponic systems because these microbes are the engines of a healthy aquaponics system.

Microbes oxidize ammonia, assist in nitrification and mineralize materials like iron in order to foster healthy plant growth and a healthy system overall.

The world of microbes is so extensive and diverse that it’s been estimated we have identified less than 1% of microbial species. Our understanding of the microbial life in aquaponic systems is infinitesimal. Dr. Storey said,

“When you figure that a shovel-full of dirt contains a hundred times as many bacteria as we know about… well, we know about as much about microbes as we do the other side of the galaxy! I’m convinced that there are all sorts of other amazing things happening in these systems that we just have no idea of, because they're all done by microbes that we can’t culture, that we have a hard time surveying, understanding.”

There is very little that we really know about microbes, although we can observe the results of their collective presence in our aquaponic systems.

In Freeport, we maintain all the surface area that microbes flourish on and are very careful not to disturb them when ever we maintaining or care for our system.

6. Water Flow

You should aim to flow the entire volume of your fish production area through the system as regularly as possible. Water exchanges are important. 

In Freeport we operate an 900 gal per hour sump pump which allows us to completely exchange the water in our fish production tanks every two hours. When water flow is balanced, they system is balances and the water quality is at is optimum. We always see excellent performance, both in the way our fish feed and the plant roots develop when our water quality is at its optimum.

Have you noticed that, so far in this series, we haven't touched on system water temperature, system pH and nutrients like iron and calcium which plants require. I'll get there soon.

My Aquaponics Journey.
With love from Freeport,