Frequently Asked Questions

1. What is aquaponics?

   It is growing fish (aquaculture) and growing plants in water (hydroponics), combined into a recirculating aquaponics system. There are many systems that claim to be aquaponics but simply use fish tank or pond water to irrigate plants; usually a good idea, but not the same thing at all.

2. Is aquaponics difficult to learn or hard to do?

   It would be, if you had to reinvent it yourself. Because there is a large body of usable knowledge available, and many successful practitioners willing to share their knowledge, learning aquaponics is easy. It's kind of like math; when you first started working with those numbers (remember, you were only three feet tall?), it was hard adding 3 and 6. Now you do it without thinking about it.

   In practice, it's just feeding the fish, planting and harvesting the vegetables. We don't spend much time thinking about the nitrifying cycle or ammonia levels. Even if we did, those things are simple to measure and understand. The hardest thing we've found about aquaponics is that so many people are interested in it. We had to start giving regular farm tours every Saturday because we had fifteen to twenty people showing up at odd times during the week to see our farm, and so far over 1,000 people have come to see the farm since we started giving tours in June, 2008!

   Remember, we are not farmers, or even gardeners. This is a really easy food production method - so easy that we don't like to use the word "farming" to describe this; as that word is automatically associated with hard physical labor.

3. What is the most important thing to know about aquaponics?

   That it's not about raising fish! Although the fish in aquaponics systems attract the most attention, the fish portion of the operation is costly both in terms of consumables and labor, and does not produce a profit unless combined with the vegetable income. Based on our last two years experience with commercial systems, the fish portion brings in 8% of the total income, while the vegetable portion brings in 92%. The problem with this is that the fish part of the operation creates a large percentage of the operating costs, for fish food, electricity for aeration, and labor for feeding, breeding, and harvesting the fish; while bringing in the small income percentage noted.

   When you try to grow MORE fish in the temperature range we are farming in (70-76 degrees F), with the fish food costs we have ($0.90/pound), the electricity costs we have ($0.44/KWhour), and the labor costs we have ($12/hour or more), EVEN with the price we're getting for our fish ($5/pound) the more fish we try to grow, the MORE money we LOSE on the fish part of the operation. This means that if you are considering commercial aquaponic production, you should get accurate numbers for fish production from a farmer in your area rather than just stick an income number into your spreadsheet. If you ever hear a consultant who tells you can grow "X" amount of fish in the system they design, you have just heard a completely misleading statement; because the amount of fish you can grow in any system is entirely dependent on the system water temperature (plus MANY other factors they often forget to mention). Aquaculture businesses that have failed outnumber those that survived by ten to one.

   A lot of people selling aquaponics system information or "kits" know how important the fish production is to potential operators, and often vastly over-state the amount of fish it is possible to grow with these systems (they all too often over-emphasize the vegetable production too), in an attempt to appeal to buyers and sell more stuff. If you hear these kinds of claims, ask the sellers to back them up with phone numbers of real users you can call to verify the claimed "fish production" and "vegetable production". You can't ever get something for nothing, or as a famous author once wrote: "TANSTAAFL!"

4. What kinds of aquaponics systems are there?

   There are all kinds of aquaponics systems out there. It is important to be able to discern which is which:

   Experimental systems: Useful experimental systems are put together with best current knowledge of aquaponics technology using established scientific methods to investigate a new idea. If the hypothesis being investigated in the experiment proves out by improving production and efficiency, or lowers the cost of a system, it is no longer an experimental system, but a successful next-generation system. If the experimenter is not using current knowledge and good scientific procedure, you may have a voodoo system, not an experimental system.

   Hobby Systems: A system built and operated with no requirement for financial return is a hobby system. Even if you want a hobby system rather than a commercial one, being well-informed about aquaponics will ensure that you have a good hobby system that is fun to own and operate, rather than a money-sucking, bad-smelling, backyard disaster on your hands.

   Demonstration Systems: A demonstration system shows how the principles of aquaponics work, and is not necessarily a profitable system, or even one that is stable over time. One might see this type of system in a school, for instance, where they wanted to teach aquaponics but could not afford or did not want a system that would require tending. Not everyone needs the 300 pounds of produce and 5 pounds of fish a week a system of a couple hundred square feet can grow. We have built a tabletop demonstration system and use it at public events, but we do not rely on it to grow the food that we eat.

   Useful Systems: A useful system is one that pays its operating costs (fish food, electricity, seeds and planting media). We offer plans for three different sizes of systems that satisfy these criteria. Whether it's a commercial system, a large family system or a micro aquaponics system, they all grow the same amount of vegetables for each square foot of raft area. A good way to determine if a system you're considering building will produce is to get references from someone who has run one (not just the sellers of the "kit") and see if it meets your needs.

5. I already have a pond/tank/swimming pool. Can I use it as part of a recirculating aquaponics system?

   A recirculating aquaponics system is a complete system, just like a car is a complete system. A car works because it is complete and has all its parts. If you just have the front wheels of a car, it doesn't do you any good. In the same way, only having a pond/tank/swimming pool doesn't do you any good if you don't understand how aquaponics systems work. You've only got part of the system.

   It is theoretically possible to use a pond as part of an aquaponics system. You will have some problems: the nitrifying bacteria that make a recirculating aquaponics system work are light-sensitive and may get killed off or severely inhibited by the light entering a pond, therefore you will need to shade your pond. You will probably need to mechanically aerate your pond to attain reasonable dissolved oxygen levels (DO). Harvesting fish out of a pond requires a seine net, a wetsuit and booties, and a much larger labor commitment than harvesting out of a tank or raceway.

   If your pond has flow-through water from a source such as a spring or creek, you will need to disconnect it from that source, install a recirculation pump and hydroponics of some sort, then shade the pond to even have a chance of it working. Flowing water through the system from your source (then dumping it out the far end of the hydroponics) won't work because the continually flowing water will dilute any nutrients the fish do deposit into the pond to a level that will probably not do the plants any good.

   People also ask if they can just put the rafts on top of the pond or tank. Except for the fact that a fish tank or pond can support about ten times the area of hydroponics trough as fish tank area, this idea will work IF you figure out a way to protect the vegetables from being eaten by the fish, and a way to feed the fish when the top of the tank is covered with hydroponics rafts, then it might work, and you might get one-tenth the amount of vegetables you would get with the same size fish tank and amount of fish put together with the proper amount of hydroponics. But this is doing it the hard way.

6. I already have a pond/tank/swimming pool. Can I just use it to grow fish without having to do this aquaponics stuff?

   Again, this is about understanding the system. Fish need several things to flourish and grow, just as any other animal does. The first thing that limits fish growth and production is usually dissolved oxygen levels (DO). This is the amount of oxygen present in the water that is available for the fish to breathe. If the fish are having trouble breathing because DO levels are low, they get stressed and don't feed or grow well. Bringing DO levels up requires mechanical aeration or flowing LOTS of water through the system. If you flow-through, the water needs to be naturally aerated (well water often won't work), and you need to put from 10% to 200% of the total system volume through PER DAY to keep the fish happy, depending on how many fish you have in your pond/tank. In other words, you need free water in order to do this. If you don't have free water, a mechanical aeration system of some kind is necessary to get enough air to the fish.

   The next thing that limits fish growth and production (after you solve the aeration problem) is water quality. The fish effluent in a well-aerated (but stagnant) pond or tank has nowhere to go, and the fish get stressed and die. It's as if your bathroom was in the corner of your living room but there was no toilet. It would get pretty pungent after awhile and you would move out or do something about it. But the fish can't. So it's necessary to clean the water somehow. This is the situation that led to aquaculture pioneers inventing biofilters for recirculating aquaculture systems (which still require 10-20% of new water a day to work), and then led to aquaponics pioneers inventing recirculating aquaponics (which doesn't).

   As an example, a 3,000-gallon fish tank with no aeration and no biofiltration might support 40 to 50 1-1/2 pound fish; the same tank with the optimum amount of aeration added might support 80 to 100 fish, but the water quality would get iffy; the same tank included as part of a recirculating aquaponics system with optimum aeration supports 1,000 1-1/2 pound fish. We know, we have several like this. So the answer to this question is about understanding the system. You can't raise fish economically in stagnant ponds or tanks.

   One more thing: depending on the fish species you have, there may be more factors in play that just these. We raise tilapia, which will breed like crazy in an open pond. After a year or two, what you'll have in an open pond situation with these fish is a bunch of 6-to-8-inch long fish, a FEW one-pound size (Biggies!), and a lot of little fish getting eaten by whatever's around, including their larger siblings. However, if you know tilapia psychology, and crowd them by putting a lot of them in a tank or in cages in a pond, they stop breeding activity and get fat instead. Because breeding consumes food and doesn't promote fish growth, by stopping it you will get fish growth and better utilization of the feed you feed them.

7. Can I do aquaponics with pigs/chickens/rabbits, or include them somehow in my aquaponics system?

   The problem here is E. Coli. For humans, there are 13 very irritating strains of E. Coli and one that can kill us. All come from warm-blooded animals (pigs/chickens/rabbits), which fish are not. Although there is E. Coli everywhere, and there are thousands of different strains, the ones fish generate are not the ones that harm humans. I know, I drank a couple of quarts of aquaponics system water. It was lucky I told my wife (the biologist), after I drank the water, she would have squashed the idea flat if I'd told her before.

   There is really no way to include these animals in an aquaponics system. The standard organic rules for animal manure require that a field have at least 120 days between the last application of animal manure to it and when harvesting occurs in order to safeguard the consumer's health. So you can use these animal manures safely in dirt farming if appropriate times are observed between manure applications and harvesting.

8. How often do you exchange the water in the system or have to sterilize it?

   Because the recirculating aquaponics system is a dynamic mini-ecosystem, it has a tremendous degree of stability. When changes occur in pH, nutrient level, ammonia levels, and other indicators, they change slowly over a period of days or even weeks. When changes do occur, such as pH getting increasingly acid, the correction is easy to administer. We have never had a fish or plant disease episode in a year of operation in the tropics.
   Our current two-part hypothesis explaining this is:
   1. Because the water quality in the recirculating system is so high (low levels of ammonia, nitrites, and nitrates, and a high level of DO) the fish are supported in having naturally strong immune systems, and
   2. Because the plants are getting an organic, chemically complex nutrient solution from the fish effluent water, they are healthy and don't develop or harbor diseases as easily as hydroponic plants grown with man-made chemical nutrients do.

   This question is usually asked by those with experience in hydroponics, where systems often have to have water exchanged and be sterilized in order to prevent rampant plant disease problems. When Dr. Rakocy (UVI) goes to hydroponics conferences, the other attendees (people with years of experience in hydroponics, but no aquaponics experience) refuse to believe him when he says he has never exchanged his system's water or sterilized it.

9. How do I get the fish to start my aquaponics system, and how do I get them from the hatchery to my location?

   Here are the applicable sections from our course manual: You don't need tilapia at first if they're hard to get, even if that's what you plan to grow. You can put in a mixed bunch of koi, catfish, and tilapia, as long as the smallest ones you put in are not so small that they are edible by the biggest ones you put in. The vegetables are 90% of your income anyway, you only need fish to excrete in your system to provide fertilizer for the plants. Sort them out later with a net and have a barbecue. If you are not in Hawaii, there are many other species of fish that are cultured commercially, grow quickly, and can easily handle the water quality of aquaponics systems. Species that would work well are yellow perch, bluegill, crappie, large mouth and small mouth bass. In Australia or elsewhere in the world there are with wild-sounding names we only barely know about that would work just fine.

   Check with your local aquaculture extension agent at the local University; they will be able to give you the names of aquaculturists' in your area you can purchase fingerlings from.

   You just need to be a little inventive to get them (alive and in good shape!) from the fish hatchery to your place. They need water, and they need air. The simplest way is to borrow a friend's pickup truck, lash a couple of heavy-duty garbage cans in the back (make sure they have good lids!), and get yourself a couple of 12-volt bait-bucket bubblers with the bubbler tubing fed through a small hole in the lid of the trash can. Put water from the aquaculturists' tanks into the trash cans (NOT fresh chlorinated water; you'll choke the fish!), put a MAXIMUM of 15 lbs of fish or so into each trash can, turn the bubblers on (make sure the airstones are well-sunk to the bottom of the trash cans and are emitting a good solid stream of bubbles), lash or tape the lids solidly onto the cans, and head for home!

10. Whom do I trust for aquaponics advice?

    Consultants will try to sell you consulting; amateurs will stun you with their lack of knowledge; and academics want more than anything to get that next paper in a prestigious publication. They all have their good points: a good consultant can solve an expensive problem cheaply; amateurs started the aquaponics movement in the first place (they were ALL amateurs back then); and there is an amazing amount of good information available thanks to all the academics who have studied and published over the years.

    Professional aquaponicists are people who make a living from operating aquaponics systems. They combine the best traits of consultants, amateurs, and academics with the ability to figure out how to make things work at a profit. A professional often has more practical and useful advice to offer than a consultant, because they have more hands-on experience with the subject. A professional exhibits the most valuable trait of amateurs: an amateur will try anything. The professional has the willingness to give unlikely things a try, guided by their knowledge. And a professional is always interested in the next bit of knowledge and understanding, just as academics are. The difference is that the professional's focus is on the bottom line, and how to make their efforts more profitable. True sustainability is when you're still in business a year from now.

    When you're listening to someone talk aquaponics, see if you can figure out their angle and interest in the subject. If you know, then you can filter out and separate the useful and economically sound information from the sales pitches, dumb ideas, and too-complex-to-be-useful data.

    If you are going to invest your time and money in an aquaponics project, then check out existing operations first. A lot of "Aquaponics" on the Web is computer-generated renderings of greenhouses and fish tanks showing systems that have never been built. If that's all you need, there are cheaper places to get them than these sites, and many places to get better information too. Actual pictures of the UVI aquaponics system on their website was what got us into the UVI Short Course in the first place. Every photo you see on our website was taken at our farm, and is something we built and operate ourselves.