Glossary of Terms and Definitions

Note: this is a constantly evolving document. WE know what we mean, right? But if YOU find an aquaponic term that is the least bit confusing or you don’t understand, and it’s NOT in this list, please leave a comment asking for it to be added. As Captain Picard says: “Make it so!”.

Now, having said that, there are some other words in our blog posts you will want to pay special attention to:

IMPORTANT: This means it WON’T work if you don’t do this, and WILL work if you do.

WARNING! This means you will be cleaning up a mess if you ignore the advice here.

CRITICAL! This means death and destruction may loom for your fish and vegetables.

DANGER! This means YOU are risking injury or death if you ignore this information.

• Allelopathic: An allelopathic plant is one that secretes and/or broadcasts chemical compounds that are actively inhibitive to the growth of plants around it. Look under any redwood tree: you will find very little weed growth among the redwood needles because they are allelopathic. An example in aquaponics systems is tomatoes. If any other plant’s roots are touching or nearby a tomato’s roots (except basil, which doesn’t seem to mind), the other plant will do poorly and perhaps even die from the contact.

• Ammonia: A product of the decomposition of organic material by friendly bacteria (our little buddies!) and a precursor of nitrogen-bearing compounds that nourish the plants in an aquaponics system: they use them for fertilizer.

• Aquaponics: Combining recirculating aquaculture with hydroponics to reduce costs, increase efficiency, and grow both fish and vegetables in the same system.

• Aquaculture: Raising fish only using commercial techniques.

• Attenuate: When a plant grows tall and spindly instead of “bushing out” as it normally would; this is an indication the plant is not getting enough light, and/or is planted too densely.

• Biofilter: Something you don’t need to “install” in one of our low-density systems because the plants are the biofilter. Lots more on this throughout this manual. Don’t waste your money!

• Biomass: Means the total weight or amount of an animal or plant in a system.

• Biosecurity: Means not bringing live stuff into your system from outside that will cause problems. Crawfish, duckweed, vegetarian water snails that eat roots, or piranha in your aquaponics systems would all be examples of poor biosecurity.

• CFM: cubic feet per minute; this is a measure of how much air a blower or air pump puts out, and is also a measure of how much air an airstone can blow out into the water. CFM and inches H2O are interrelated, because it takes more work to put out air in deeper water. There is higher water pressure there so you need to provide higher air pressure to overcome it and push the air out of the airstones in deep water.

• Chlorine/Chloramine: These are indicators of how much chlorine is in your water; chloramine is a related chlorine compound that has the same effect on fish and plants. Measured with test strips before putting your fish in the water or adding the water to existing systems.

• Coir: Ground-up coconut fiber used in potting mix. Used because it is sterile and doesn’t harbor deleterious bacteria and fungi the way (supposedly sterile) peat-based potting mixes often do. Mix 60/40 with vermiculite to make potting mix.

• DO: Dissolved Oxygen is an indication of how much oxygen is in the water and available for fish to breathe, AND for the plant’s roots (they need oxygen also to grow well). It is measured in ppm or percentage with a DO meter or test strips.

• DE: Diatomaceous Earth; this stuff is basically ground-up chalk. It’s chalk dust! But it kills all kinds of hard-shelled bugs, including centipedes, ants, aphids, and others that will cause you problems. Lots of info on how to use it in our Pest Control Section.

• Experiment: A valid experiment is when you change one thing only in an aquaponics system, and have another identical aquaponics system (except for that one thing) right next to it to act as a control. The control system is your reality check; if something is radically different in the experimental system as compared to the control system, then you can be fairly sure that the one thing you changed was the cause of the difference. If you simply change one thing in your one system, but don’t have a control system, you can’t be sure that the difference in results was due to the change or some other environmental variable that you just didn’t notice.

• Flow Rate: How much water a pump puts out per minute specified in gallons per minute (GPM) or gallons per hour (GPH), or the rate of flow in a pipe or trough.

• GPM and GPH: Gallons per minute, gallons per hour. To get GPH from GPM, multiply by 60. To get GPM from GPH, divide by 60.

• Head: The vertical distance a pump needs to lift water. Lifting water to a higher “head” requires a larger-capacity water pump that will use more electricity than lifting water to a lower “head”. If your system is on a hill, you will need to install a higher-capacity pump than the pump that same system would use if installed on level ground.

• Hydroponics: Growing vegetables with water in sterilized soil-less systems (many different kinds are used, some with soil substitutes).

• Inches Of H2O: A measure of air pressure at relatively low pressures. For example, if you have 10” H2O air pressure, the air will come out of an airstone that is 10” deep in your water, but not out of one that is 12” deep. There is 12” of water pressure at the 12” depth, and 10” of H2O pressure is not enough to overcome the water pressure at that depth. One pound per square inch (1 PSI) is equal to a pressure of about 27 inches H2O.

• Mesh Pot: Is a small plastic pot without a LIP (important!), made of mesh in the sides that plant roots can drop down through easily into the water when planted in an aquaponics system raft. Only they are evil, lipless pots, and will fall through the holes in your rafts! Don’t mistakenly buy these! We use Poppelmann slit pots.

• Nitrates: Are the nitrogen-bearing chemical compound that is the primary nutrient for plants in an aquaponics system, and is the product of Nitrobacter, a nitrifying bacteria that metabolizes nitrites and excretes nitrates. Some microbiologists are now saying a bacteria called Nitrospira is really the one responsible for making nitrates out of nitrites; we’ll let them figure out which is which!

• Nitrifiers/Nitrifying Bacteria: Nitrifying bacteria that are present in soil and water. These bacteria metabolize (eat) ammonia from decayed organic material and turn it into nitrites (a form of nitrogen that can be used to a certain extent by plants, but is toxic to fish), then into nitrates (a form of nitrogen that is much more usable by plants, and is less toxic to fish than nitrites). Nitrifiers are light sensitive, that is, too much light kills them or inhibits their growth.

• Nitrites: The nitrogen-bearing chemical compound that is the food source for Nitrobacter (the nitrifying bacteria that produces nitrates), and is the product of Nitrosomonas, a nitrifying bacteria that metabolizes ammonia and excrete nitrites.

• PPM: A unit of measurement that means parts per million. This is exactly the same as milligrams per liter (mg/L).

• Raft: This refers to the 2-foot by 4-foot (or other size) of Dow Blue Board Styrofoam sheet used as rafts to hold vegetables in mesh pots for growing in an aquaponics trough that we started with. We have now standardized on specifying systems in terms of square feet (easily convertible into square meters), as many different raft sizes may be used depending on the purpose of the system and the owner’s preference and experience during the “test grow”.

• Recirculating: A closed system that uses the same water over and over again by pumping it through the tanks/troughs of the system.

• Slit Pot: sometimes mistakenly referred to as “mesh pots”, these have lips and won’t fall through your raft’s holes. If they do, you probably purchased the evil lipless mesh pots by mistake.

• Tank: Usually any aboveground vessel made to house and raise fish.

• Troughs: Usually on-ground (because of their weight of one ton per 8 lineal feet) lined structure of some kind that holds the water that your rafts that grow vegetables float on top of.

• Vermiculite: An expanded product made from mica, a naturally occurring mineral. It is non-toxic, lightweight, and provides aeration in potting mix when mixed 40/60 with coir.

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