Fundamentals #1: The Fish and Plant Factory

Aquaponic FactoryThis post outlines the first of two fundamental principles for operating an aquaponics greenhouse in the cold.

Principle #1: Aquaponics is a system of connected components with different needs.

In other words, aquaponics is a factory, not a house. First, some background:

How We Think Matters

I often see the following question on the aquaponics forums:

How warm do I need to heat my greenhouse to keep my fish happy? A reasonable question, right?

Well… it is and it isn’t. This question stems from the fact that we live in buildings with heating and cooling systems designed for a single purpose: keep the air in the space at a comfortable temperature.

When you go on a furnace website, they invariable show a picture of a nice family sitting in their living room, warm and happy and smiling with their comfortable air temperature.

But fish don’t have couches. They don’t smile. Fish spend all their time in one room, and that room is filled with water. If they met their children, they would eat them.

The way we think about heating a fish and plant house is entirely different than the way we think about heating a human house.

Buildings vs. Factories

In my day job, I work with energy efficiency in buildings and factories. These two building types operate under two completely different philosophies in terms of heating and cooling. In occupied commercial or residential buildings, the exterior walls or shell provide the only layer of protection against outdoor conditions. You control temperature in the same way for the entire interior or “envelope” of the building.

In factories, however, temperature and humidity control vary dramatically depending on whether you’re smelting aluminum, processing potatoes, or creating liquid nitrogen.

Within the building shell, many additional layers of thermal protection provide the right conditions for people, materials, and processes.

When you get down to it, an aquaponics room or greenhouse acts more like a small factory than a occupied building. It doesn’t need to be maintained at temperatures designed for humans. Different parts of the system require different temperature conditions. Separating the different system components with thermal barriers allows you to maximize energy efficiency by providing only the needed energy inputs required by that component.

Single Tank, Single Bed DWC System with a Filter

Single Tank, Single Bed DWC System with a Filter

An Aquaponics System can be Broken up into the Following Zones:

  • Fish Zone: The fish tanks require a certain minimum and maximum temperature, and can tolerate a limited range of daily swings, depending on the breed of fish.
  • Transport Zone: The pumps, filters, and piping require a different temperature profile in order to prevent freezing.
  • Root Zone: The root zone of plants requires a third temperature profile, which allows for root growth, depending on the type of plant.
  • Nitrification Zone: In this area, nitrifying bacteria convert toxic fish waste into non-toxic plant food.  To do this, temperatures must be maintained above 50°F. In flood-and-drain systems, the root zone doubles as the nitrification zone.
  • Leaf Zone: The above-ground portion of the plant requires a final temperature profile and swing limits, again depending on the type of plant, its sensitivity to frost, and the expected growth rate.

All of these subsystems interact, but each holds different requirements and needs different levels of protection.  Sure, heating the greenhouse, as our question suggested, solves all these problems, but when nighttime temperatures hit negative 20°F this will break the bank and burn a lot of coal, gas, or wood to make all that electricity. Treating these zones differently offers us the opportunity to save a lot of energy.

Principle #1: Aquaponics is a system of connected components with different needs.

Next week I’ll discuss Principle #2: To save energy in aquaponics, you must manage enthalpy.


10 responses to “Fundamentals #1: The Fish and Plant Factory

  1. Nice. You just step up to the plate and hit that one out of the park. You have my attention. I am looking forward to the details. I just happen to have a couple of walking coolers that I didn’t know what to do with. Now I’m thinking I will keep them close at hand.

    Liked by 1 person

    • Thanks onyxtacular!

      I’ll have a kit for converting freezers to tanks available as soon as I’m confident that it’s permanently reliable. Finding a coating to water seal them is proving challenging. Currently trying various industrial products.


      • what about so clamps around the outside? I saw a guy on youtube that made some clamps for his diy wood gassifier. I’m thinking if it’s good enough for hot gas it should keep water at bay.


      • I’m not familiar with SO clamps. Looks like they’re used for welding? Is that right?

        If you use a freezer, it is already really pretty well sealed. Did you have a different kind of tank in mind?


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