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Friendly Aquaponics Newsletter
Number 31
March 8th,  2011
Images from our farmily aquaponics farm
Aloha Friend,

Here we are again! A week's gone by: we're older and wiser, and of course, we ALL have more money in the bank
! While I was putting all our money in the bank, I talked to our bank teller, and told her my goal in life was to keep getting older for as long as possible. She knew exactly what I meant, and we instantly had a connection. In Hawaii, the land of aloha, it's easy to remember this and take time to connect with the community around you. In Hawaii, we pull over and ask people stuck by the side of the road if they need help. We share our food and resources with those less fortunate than us; this is a very Hawaiian thing to do.

Our attitude about strangers is Hawaiian: in ancient times they would classify a newcomer as either a family member or an enemy. We always assume the best about a person (that they are a family member) and give them plenty of chances to prove us wrong. There are few we don't consider family. Imagine what the world would be like if everyone treated people the Hawaiian way!

We and seven of our students have the first USDA organically certified aquaponics farms in the world! If you want to learn how to build an organic aquaponic system instead of just read about it, we have trainings in Florida in March and Hawaii in April of 2011.

The Florida training will be held March 21st to March 24th, 2011 at the Community Center of Ridge Manor, 34240 Cortez Blvd, Ridge Manor, Florida. Susanne Friend and Tim Mann of Friendly Aquaponics will be teaching the course  with Friendly Aquaponics affiliates Tonya Penick and Gina Cavaliero, who own and operate Green Acre Organics, where the hands-on sessions will be held. These trainings will be held at Green Acre Organics on a regular basis from now on. The conference room we've hired for the Florida training only holds 120 participants, so reservations for the course will be taken on a first-come, first-served basis.

If you're interested in commercial scale aquaponics, please take a look at both the Hawaii and Florida Commercial Aquaponics Trainings (Special Offer in right sidebar of this email), where you will learn more about real-life operation of a commercial aquaponics system than you can anywhere else in the world. For smaller home backyard and apartment systems, please read on:
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Purchase Construction Plans and Operating Information for 4 Different Sizes of Apartment/Condo Aquaponics Systems $49.95

Our Apartment/Condo System package includes new and easy-to-understand building instructions and complete operating information for 4 different sizes of small aquaponic systems based on our years of experience operating a commercial aquaponics farm. Anyone can build a system out of plastic barrels, but operating one successfully without good and easily-understood information can be frustrating. You simply use the "Daily Operations Checklist" in the manual and follow the step-by-step instructions on your way to success.

We spent hundreds of thousands of dollars, hundreds of hours, and built our first commercial aquaponics systems with FAR less information than this manual contains. We included all the information learned from that experience in this manual so you don't need to make any of the same mistakes we did.


Learn about our Apartment/Condo Systems!


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Aquaponics Nugget #31:
Aeration In Aquaponics Systems (Part 2)


Last week we talked about the three interdependent factors that influence how you adequately aerate an aquaponics system: amount and location of aeration supplied in both fish tanks and troughs; water flow rate in each trough and length of the trough; and water temperature. We did a test in which we drastically reduced the water flow rate in one of our systems, and added aeration in the troughs. Even though we had to add a small amount of aeration in the troughs (which consumed more electricity to provide), the water pumping used so much LESS electricity at the lower rate that we had a 30% overall savings in energy required to run this system, and had even HIGHER DO's in the troughs and fish tanks than before.

After this positive test result, we installed airstones in our largest system, which has three separate sets of troughs connected to it. Because it takes awhile to install airstones in the troughs, we put them into one set of troughs at a time then turned them on. Each time we added airstones to a set of troughs, it raised the DO in the entire system, including the fish tank AND all the other troughs! Also, the DO was DURABLE; meaning it stayed higher everywhere, even when it was only added in one place.

Our observations indicate that poor vegetable growth ends and good growth begins somewhere between a level of 3 to 3.5 ppm DO in the troughs. We feel an adequate DO level in the troughs is 4.0 or above, measured where the water EXITS the trough, and 5 ppm or above is GOOD. We confirmed this by running a system with plenty of nutrients and water flow rate as low as 2 gpm through the troughs, but NO airstones in the trough; we saw decreased growth in this test system. As soon as we added air to the troughs, plant growth exploded, indicating that the most influential limiting factor here was the lack of air in the troughs and not nutrient levels or flow rate.

You can determine if you need aeration in your troughs by measuring the DO going into the trough, and going out, but the system must have mature plants in it for this to be useful information. Plants use oxygen, right? If you only have a bunch of little sprouts in your system, they will be using a smaller amount of oxygen than when they are fully-grown and your system is in a mature condition. Measure your DO when you have a system with a normal range of some sprouts, some middle-sized plants, and some mature plants in it for accuracy. We’ve seen the aeration requirements and DO change radically in system troughs in relationship to the size of the plants (biomass) in them.

If you have a mature system, and have 5.0 ppm DO (or under) going into a trough, and 2.0 ppm DO in the water going out of the trough, your plant growth would benefit hugely from some additional aeration in this trough. If you have 5.0 (or more) going in and 4.0 (or more) going out, you are just fine and additional aeration probably won’t make any difference. Even if you think you won’t need air to your troughs, to be absolutely safe, run airlines to the head of all your troughs when you are building your system. Then the air is there if you need it.

How do you achieve an adequate level of aeration in your troughs; is there a formula for the amount, size, and spacing of airstones? It’s not that simple, and YOU have to figure it out for YOUR system: it will vary for every water temperature, plant species, and system, depending on many INTERDEPENDENT factors. In other words, if you change one item affecting aeration in your system, it has the potential to change every other aeration item in the system. So, back to the original tenet of aquaponics: UNDERSTANDING THE SYSTEM. If you are just building your system, OR you have an existing system and you’ve measured the DO exiting your system troughs and it is LESS than 4.0, you need additional supplemental aeration in the troughs. Here’s how you do it:

Plumb the system with a 1” airline to the head of each trough with a 1” valve on it, and install a 1” airline along one side of the trough, right up against the liner at water level INSIDE the trough. This valve is important because you MUST be able to adjust the amount of air going to each individual trough’s PVC airline. If you have four to six troughs hooked up to a single supply airline, and NO valves, the air will pick the EASIEST airline (with the least resistance) to exit through, leaving no air going out the airstones in the other troughs. The valves at each trough allow you to adjust the amount of air going to each trough by “choking down” the air going to that trough so it is evenly distributed.

IMPORTANT! Even if you only had a single trough, you would still need this valve installed on its airline to adjust the air anyway. Here’s why: it’s so much easier for air to get out through airstones in 10 inches of water than it is for it to get out through airstones in 40 inches of water (in the fish tank), that unless you can choke it down here, it will all come out here in the troughs and NONE will go to the fish tank. Choke down the 1” valve at the trough until you can see a good stream of bubbles coming out of the airstone that is FARTHEST down the airline away from the valve. This is how you know it’s adjusted just right to create optimum DO’s. When you have each individual airline adjusted this way, re-check the last airstone in all the troughs, you may need to re-adjust the valves to fine-tune it because changes in one trough may slightly affect the others. If you have more than one system running off a common air manifold, re-check the other systems too, because changes you make in this system’s settings will affect them all.

We have 78-foot long troughs, and we start by putting four AS8L airstones (Aquatic Eco catalog number) on this line at ten-foot spacings, AT THE END OF THE AIRLINE NEAREST THE WATER INFLOW FOR THAT TROUGH, with the first airstone located ten feet from the inflow end of the trough. This way, the air is going into the water as soon as it enters the trough, and the DO generated from this persists to the end of the trough and beyond. Then we let the system run for a day or so to let the DO levels stabilize and remeasure DO’s in the troughs.

IF, after we’ve done this, we find DO is not in the desired range (4-6ppm), then we add airstones one at a time to the PVC airline until the DO reaches the desired range. We put our first additional airstone (if needed) in between the 10-foot and 20-foot airstones, the second one between the airstones at the 20-foot and 30-foot airstones, and so on. DON’T put airstones in near the OUTFLOW end of the trough, you’ll probably be wasting electricity! If you measure DO, find that it’s low, and need to install these additional airstones, put them in as explained here: between the middle of the trough to the inflow end of the trough, NOT near the outflow end.

How to install airstones in the troughs!  We drill and tap an Aquatic Ecosystems 62006 fitting into the PVC airline every ten feet so it is facing down at a 45-degree angle towards the bottom of the trough. We install the BTV40 ¼” airstone tubing onto this 62006 fitting, and put a ¾” plain STEEL threaded nut (NOT GALVANIZED, this brings toxic ZINC into your system) onto the airline tubing right next to the airstone to hold it down onto the bottom, because the “float” from the air inside the bouyant airline tubing is sometime enough to lift it vertically off the bottom so the airstone’s bottom can rub a hole in the bottom of the trough. You also may want to add more steel nuts on the body of the airstone tubing to keep it down on the bottom of the trough; if it floats up it can get tangled in the roots growing down from the plants on the rafts above.

We also install two DB10 airstone bumpers onto each airstone so that it won’t rub a hole in the bottom of the trough even when sitting properly sideways on the trough liner bottom.

IMPORTANT! Make sure when you put the airstone into the trough you don’t just toss it in! Get your arm wet and place the airstone gently, HORIZONTALLY on the DB10 bumpers, onto the flat bottom of the trough in the middle of the trough. Otherwise it’s possible it will end up sitting on its end and rub that hole in the bottom of the trough you were trying to avoid with the DB10’s. It will get disturbed each time you move a raft with a bunch of hanging plant roots over it, so you need to reset it every time you harvest to make sure that you don’t leave stones on their sides rubbing holes in your liner!

(Next week: "Flow Rate in Aquaponics Systems" Part 1, with information on this important and interesting topic and how it relates to aeration requirements in aquaponics systems).

Click to see our new Video!
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Free Farm Tours
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Aquaponics tour at the Friendly farm!

We hold a free workshop on our farm the FIRST Saturday of every month,  focused on growing food with aquaponics and permaculture.  Click here for information. See you there!

If you are a school, a non-profit organization, an organization working with the poor, Native Hawaiians, or ex-inmates, or if you are a church, we will hold a free farm tour for you anytime. You DO need to email us first to schedule, or we might be out on errands!


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Taro grown in a 2" net pot (little bump at bottom)



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4-month old prawn (macrobrachium rosenbergii) grown in hydroponics troughs of our aquaponics systems


Special Offer! Sign up for our April 4-7th, 2011 Hawaii Commercial Aquaponics Training OR our March 21-24th Florida Commercial Aquaponics Training now, and we will email you our Micro System package so you can begin studying aquaponics! ($99.95 value)

Sign up for Hawaii Commercial Aquaponics Training

Sign up for Florida Commercial Aquaponics Training

In The Farmily
We're usually hospitable, but sometimes have unwelcome visitors to the Farmily that we want nothing to do with. Here's some examples:

Someone gave us some duckweed to try feeding to our tilapia. He insisted "My tilapia eat a five-gallon bucket of this every day. They love it!". What we didn't find out until much later during a phone call to his farm manager was that the reason his tilapia eat duckweed so eagerly is that he doesn't feed them ANY commercial fish food. They're in a perpetual state of starvation, so OF COURSE they eat the duckweed! If you were starving you'd eat grass, or old shoes, or anything you could get.


You've heard duckweed is 38% protein, right? Well, that's on the DRY weight of the duckweed. Duckweed is about 95% water. The actual protein content of regular wet duckweed is therefore 38% of the 5% that is NOT water, which is 2%. We could have done some simple math and avoided all this trouble!

Fortunately, before we ever fed any of this duckweed to our fish (thereby introducing whatever might be in it to our aquaponics systems) we quarantined it for 45 days in a separate tank. We found crawfish in the tank at the end of that period, which had been brought in somehow with the duckweed. We meticulously cleaned the crawfish out of the duckweed and put the duckweed in another tank, then fed it to our fish. We ate the crawfish.


You want to raise crawfish? Crawfish are like piranha with opposing thumbs: they will eat anything and everything in a closed system, including each other (except any tilapia that are too big for them to eat). They can crawl out at night and traverse long distances cross-country in the cool darkness, and so will transfer themselves to other nearby systems.


If you get them in an aquaponics system the only sure way to get them out is to dry and sterilize the system. This means chloroxing everything in the system: tanks, rafts, troughs, piping, pumps, and so on, then letting it dry for a couple of days. It would be a huge job, and you would lose all that system’s productivity for a month or so. Keep crawfish out of your farm!


When we finally fed the duckweed to our fish, they didn't eat it. We fed them no other food for a day; they didn't eat it. When we starved them for two days; they finally ate about a quarter of what we put in the tanks, then stopped.

That would have been OK, score 1 for the tilapia, duckweed 0, but the duckweed spread through every system we had so that took an incredible amount of energy to eradicate it. We thought.


It keeps popping up here and there, however, and is an ongoing maintenance problem we’ll have FOREVER. Keep duckweed AND crawfish out of your farm at any cost!

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This email, our manuals and construction plans are all copyrighted by  Friendly Aquaponics, Inc, Susanne Friend and Tim Mann, 2008-2010

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Honoka'a, Hawaii 96727
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