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Friendly Aquaponics Newsletter
Number 79
June 5th,  2012
Images from our farmily aquaponics farm
Aloha Friend,

Today's newsletter is on solids settling tanks. We covered biofilters in our back newsletter "Commercial Newsletter #9".

But first, in case you missed our recent newsletters that covered organic certification:

We've written two newsletters recently about organic certification: the first was our Commercial Aquaponics Newsletter #7, which covered the basics of how to get certified, and what's involved, also how to shoot yourself in the foot and prevent your systems from ever being certifiable. The second was our Commercial Aquaponics Newsletter #10, written by Susanne, which contains a list of all the certifying agencies that currently certify aquaponics and all the certified aquaponics farms she was able to locate.

Here are some facts about organic certification for aquaponics: We were the first farm in the world to get their aquaponics systems certified organic in August of 2008. Since then, seven of our students have been certified organic.

Fact 1: Organic certification is valuable because certified produce can bring twice as much income to the farmer for the same amount of work.

Fact 2: We are the only aquaponics teachers who actually have organically certified aquaponics systems; we have been teaching USDA organic certification using them since 2008.

Fact 3: Our next scheduled live aquaponics, solar greenhouse, and commercial aquaponics trainings are in Hawaii the week of June 24-30th. There is more information on those trainings on our webpage here.

Fact 4: There is a ton of true information on USDA organic certification on our webpage here.

If you're interested in our Solar Greenhouse technology, please take a look at our Aquaponic Solar Greenhouse Training (Special Offer in right sidebar of this email), where you will learn more about how to grow affordably using aquaponics in greenhouses than you can anywhere else in the world. The next training is in Hawaii in June 2012. For smaller home backyard and apartment systems, please read on:
Purchase Construction Plans and Operating Info 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 or IBC totes, 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 also cover how to make aquaponics systems out of weird things like old refrigerators and door frames; this makes aquaponics much more economical to get started in!

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!

Aquaponics Nugget #79: The Science Of Solids Settling Tanks, Net Tanks, And Degas Tanks

Where Did It All Begin?

The first use of solids settling tanks in aquaponics began in a university setting (they had been used in sewage treatment facilities before this for years). The university people were aquaculturists originally, and ventured into aquaponics as a way to improve water quality for the fish. They had a simple goal: grow as much fish as possible in a system of a given size.

How It Works:

The water from the fish tank (where all the solids were generated) flows into the cone-bottomed solids settling tank next. Inside this tank, the fish excrement settles out to the bottom of the tank, where it can easily be drawn off daily and used for fertilizing plants in the ground. When we emptied the solids settling tank in our first system, we'd get a 5-gallon bucket of stinking black goo once a day.

Next the water flows through the "net tank", a similar tank, but filled with bird netting (lightweight monofilament netting with a ton of surface area, which is normally used for keeping birds off of fruit trees).

Although the function of the net tank was never explained clearly to us, on our farm it seemed to catch all the small suspended particles of excrement that were too light to settle out in the solids settling tank, and prevent them from going on out into the system to the plants. This tank and its netting required cleaning every two weeks to a month or so; the result was getting covered from head to toe in the same black stinking goo that the solids settling tank caught.

Next comes the "degas tank". We were taught that the degas tank, with its voluminous aeration, got rid of the carbon dioxide and hydrogen sulfide (fart gas) that the biological processes occurring in the solids settling tank and net tank created, before those gases could go out to the vegetable troughs.

So far so good; we built our first systems this way, and they functioned well. We got an eye-opener at the end of our first year though: we raised 6,000 pounds of tilapia that year, and when we ran the numbers (being business people who
have to survive off the actual income from the business, and keep numbers to facilitate that) we found we'd lost $2.00 per pound on each and every pound of that 6,000 pounds of tilapia, for a total loss on the fish of $12,000! This was a large enough loss that we ended that first year in the red, even though we'd had the income from the vegetables also.

BigTilapia1Small 2

This is a beautiful 7.4 pound tilapia; we would lose $14.60 on this fish if we sold it through the normal outlets in our area! It is one of the brood stock we use in our tilapia breeding program.

Our Low Density Systems

Everything changed for us then.
Not having a trust fund or a budget committee to appeal to the way universities do, we realized we had to find a better way to raise the same amount of vegetables on fewer fish. We developed our Low Density (LD) systems as a result, and are operating only LD systems on our farm now. We held our breath for the first few months until we realized our first LD system grew just as many vegetables as the more expensive systems with all those tanks.

What's an LD system? It is an aquaponics system that consists of a fish tank and vegetable troughs, and no other tanks, operating on one-fifth of the fish that the systems with all these other tanks do (LD systems use about three-tenths of a pound of fish per square foot of raft area). This makes the system simple and inexpensive to build and operate.

What's an HD system? It's the original university-type system, with the solids settling tank, net tank, degas tank, and uses an average of a pound and a half to two pounds of fish per square foot of raft area. What's the benefit of these systems? They grow the maximum amount of fish possible in a system this size. However, you also need to purchase and plumb the three additional tanks, and the fish tank and blower required by such a system are five times the size of the ones required for an LD system that grows the same amount of vegetables (and the blower uses five times as much electricity, forever).

The benefit of the LD systems was that they only require one-fifth the fish, one-fifth the electricity for aeration, one-fifth the fish food, and one-fifth of the labor to breed, feed, and harvest the fish. We grew the same amount of vegetables, but lost less on the fish; making more income overall.

Which System To Choose:

A common (but incorrect) assumption we commonly see in aquaponics is that one of its purposes is to grow as much fish as possible. This is great as long as you don't have to make any money from the fish, and never examine your costs to see what your fish is actually costing you per pound. Unfortunately, most of the people espousing this view have no experience with what it costs to raise the fish versus what the fish are worth, and thus, their opinions are just opinions. If they had to make money from their fish, they'd go broke.

It's easy to decide whether to use an LD system or an HD system by applying the two simple tests that follow:

If you add up your costs for raising fish (purchase price or cost to raise fingerlings, plus fish food, plus electricity, plus labor) and find that they are MORE than the wholesale price you get for your fish, the most productive and profitable system is an LD system
(because you are in an economic climate where you lose money on the fish!).

If you add your costs for raising fish and find that they are significantly LESS than the wholesale price you get for your fish, the most productive and profitable system is an HD system (because you are in an economic climate where you make money on the fish!). It's that simple. If you make an emotional decision, or a decision based on what you believe (instead of what you know to be true), then we hope you have a trust fund to finance your experience with aquaponics.

There are a few places in the world where all these numbers line up so that it makes sense to try to raise more fish. We have clients in Thailand and in Egypt who use our HD systems. Take the Egyptian one for example: they have 6 cents a kilowatt-hour government-subsidized electricity, 17 cents per pound fish food from a local cannery, $4/day labor costs, and their wholesale price for tilapia in a nearby city is $5 per pound.

For us in Hawaii, the numbers look more like this: we
have 45 cents a kilowatt-hour electricity, $1.00 per pound fish food, $120/day labor costs, and our wholesale price for tilapia is $2.50 per pound because of the cheap frozen Chinese tilapia our market is flooded with. We lose $2.00 per pound on every pound of tilapia we raise. What's our strategy? We use our LD systems to raise vegetables in, and we sell as many of the tilapia as we can as fingerlings and fry for people to stock their ponds and aquaponics systems with (because we make more money on the smaller fish), and we really make our income from the vegetables from our systems. It's that simple.

GrownOut1medium 2

Friendly Aquaponic's FIRST Aquaponic Solar Greenhouse in full bloom, Honoka'a, Hawaii, March 2012, (on a grey rainy day) showing PV panels, and growing plants.

Next week: Part 3 Pump Intake Filters where we give instructions and photos showing how to make these filters (we promised these instructions this week, but had to run a different column, sorry!). Thanks for listening!

Click Here To See Our New Aquaponics Video!
Back Issues Of Newsletters Now Available, Click Here!
Purchase Trough Liner Directly From Manufacturer!

Free Farm Tours
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!


3-1/2 pound kalo (taro root) grown in a 2" net pot (little bump at bottom)


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

Special Offer! Sign up for our June 27-28th Aquaponic Solar Greenhouse Training
or our
June 24-26th Aquaponics Technology Training, and receive a free Micro System DIY package so you can begin studying aquaponics! ($99.95 value)

More Information on Hawaii Aquaponic Solar Greenhouse Training

"In The Farmily"

Every farm has a feed room, feed shed, or feed closet where they keep the different feeds for the various animals on the farm. It is a good idea for you to make sure that the animals don't  have any idea where food comes from, as we recently found out.

It started out simply enough: one of the kids spilled a bit of feed on the ground right outside the feed room while getting some food for the chickens.  The single chicken that we hadn't been able to catch (to clip her wings so she couldn't fly over the fence) found it first.

She told all her friends about the cornucopia over at the house, and pretty soon we had eight or ten chickens who could either fly over the fence, or who found some other way to bypass it. Not long after that, we had twenty chickens at a time waiting for their train right outside the feed room, hoping more grain would get spilled.

This wouldn't have been so bad by itself if we didn't also have goats. We'd had one mother goat and her two babies grazing the grass around the house so we could keep an eye on the babies while they are small, and the mother goat found the feed room.

Now, a goat has considerably more mass and a LOT more leverage than a chicken. When she smelled what was inside the feed room, she simply pried the door open using her head.

So we remembered to close and latch the door next time. Only she had already tasted Paradise, so she simply pried the door off its hinges this time.

We got the long-awaited chicken coop finished, and put all the chickens over the fence with their wings trimmed. The baby goats got big enough to safely go out into the big pasture with the horses, and we put better hinges on the feed room doors.

You heard me mention horses? We've got three Shires, each about 2,000 pounds. Let's hope they don't hear about the feed room from the goats or the chickens, because they can go through anything!

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This email, our manuals and construction plans are all copyrighted by  Friendly Aquaponics, Inc, Susanne Friend and Tim Mann, 2008-2012

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