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Friendly Aquaponics
Special Newsletter

Special Edition Newsletter Number 9
April 10th,  2011
Images from our farmily aquaponics farm
Aloha Friend,

The responses we got to our last "Special Newsletter #8", overwhelmingly requested more information on the subject of "How do I start a commercial aquaponics farm?", so we are continuing a series on this question in the main body of this "Special" newsletter.

We also have a new column in the right sidebar: "The Fish's View". We've upset
people who consider themselves aquaponics experts, and they've attacked us in online forums. We cover the current situation in today's "The Fish's View".

And now, on to the actual useful information for today:

Losing Your Fish

An associate of ours lost all the fish in his media-based system when they died from over-cooling. This is critical to a commercial aquaponic farmer, for if you lose your fish, you've lost your fertilizer generator and maybe the farm. We'll copy his letter here so you can understand what happened, and avoid having it happen to you:


In the first newsletter, we related how the water in our media based test system was warmer than the similarly-sized deep water raft system right next to it, and suggested that i
n an extreme case this might translate into an aquaponic system that has to be shut down or artificially cooled in really hot weather if the water heats up too much from this phenomenon.

We ran our flood-and-drain trials in the middle of the summer, and noticed that e
very time the media bed "drained" in our test system, warm ambient air was brought down in between the media spaces, where it warmed the media up. The next time the bed flooded, the heat the media had absorbed from the warm air was transmitted immediately to the system water. This gave rise to concerns about the possibility of this phenomenon overheating the system.

What we hadn't fully thought out was that this process could also produce cooling effects, with potentially disastrous consequences. At least, not until we got this email from one of our students:

The Problem:

The email we got from Larry Yonashiro surprised us at first, but after considering it for a bit, it made perfect thermodynamic sense. Rather than his media system heating up the water, he had an experience with cold ambient air that apparently "cooled-down" his media bed system, to the point where all the tilapia in it died.

Larry's Email:

Aloha Tim,

Your newsletter added a new twist to a solution to a problem that I had last month with fish mortality. I lost all of my prized golden tilapia in my media-based sprouting table system. For the longest time I couldn't figure it out because everything was within acceptable levels, ammonia, nitrites, nitrates, pH, DO, water clarity, and the fish all died.

Then I checked the Kahului weather data and found that the week before, March 9th, we had the big rain and our temperature dropped to 55
°! Tilapia often experience mortality when the fish tank water gets below 60° F or thereabouts. The rain was also cold from the upper atmosphere because they had hail on Oahu. I concluded that it was the temperature because I wasn't taking the temperature readings during the rainstorm and all the water chemistry checked out OK around that time.

All the fish in my main system survived I concluded because of the larger thermal mass in the system, 4,100 gallons, kept the temperature from dropping too far (reader: he's referring to a one of our standard deepwater raft systems with a lot of thermal mass, and no media involved). But your comparison of the flood and drain media-based system versus the deep water raft system added sealed that conclusion for good.

I immediately went out and compared the temperature between my main system and the sprouting system. My main deep water raft system had a temperature of 76
° this evening, and my flood and drain sprouting system had a temperature of 72°! Air temperature is now 73°. The flood and drain system, besides having less thermal mass, is more sensitive to temperature changes in both directions!

[Note to reader: Larry took this water temperature measurement at the end of the day, when the media-based flood and drain system would be at its warmest, and it was still colder than the ambient air temperature. It could conceivably get much colder than this overnight, because the system continues to cycle while the air temperature drops all night long. If his media-based system followed the same temperature profile during the night, Larry's water temperature could easily have gotten down to or even slightly below the 55
° air temperature that was recorded].
Because of this, I'm getting some koi for my flood and drain sprouting system, since they should handle cold weather better.

Thanks so much for all the valuable advice you so freely give.

Aquaponics No Ka Oi
(Hawaiian for: Aquaponics Is The Best)

You can read Larry's complete write up this event on his website's blog at There's also excellent information in the blog about salt treatment of fish for disease, and why you should never put salt in an aquaponics system.

Analysis and potential solution:

Larry (and his wife Patty, the vegetable expert in the family), have a lot of experience with deep water raft systems, are familiar with water quality parameters and did substantial data logging during this event. They have a lot of experience with these fish. I trust their observations, for they were there when this event happened, and are scientific, watchful, and meticulous.

After reviewing the weather data on Larry's blog, I am reasonably certain there was no other factor besides the cold night-time air which cooled down the media, which then cooled down the system water, that caused the fish to die.
The conclusion we've both come to is that media-based systems can over-cool system water to the point that your fish die. Larry is planning to solve this by using koi in this system, which he feels can handle lower water temperatures than these tilapia.

Another thing you conceivably could do to minimize the risk of killing your fish in a media-based system such as this, when the nighttime temperatures drop too low, is to put your water pump on a timer so it turns off just before dark. This would keep the relatively warm water in the fish tank in the fish tank, and not send it out to the media bed to get chilled down during the night. This would work only IF you were certain your plants and media bed would not be harmed by turning off the water flow during the nighttime. It would at least reduce the cooling effect of the ambient air on the media/system water during the coldest 12 hours out of every 24.

More thoughts about media beds:

We had others respond to this subject as well: another reader thoughtfully pointed out that the mosquito eradication function of a deepwater raft aquaponics system (click here to read more about how deep water raft systems can eradicate mosquitoes) may not work in a flood-and-drain system, because there is always a small amount of water in the bottoms of the media beds that would keep mosquito larvae alive, even when fully "drained".

The mosquito fish cannot survive in between the media (hydroton, cinder, or expanded shale) in the bottom of the flood-and-drain beds; because they are very sensitive to abrasion. No fish does well when it is frequently bumping into rocks; it removes their protective slime coat and they die in short order, and mosquito fish are no exception to this.

We love our mosquito-free farm! This is a biggie for us; we live on a seven acre farm on the wet windward coast of the Big Island in Hawaii that has NO mosquitoes. We can leave doors and windows open all day, and never get awakened by that infernal buzzing in the ears in the middle of the night. We love our deep water raft system, and we really love not having any mosquitoes. As long as we keep water out of places we have no mosquito fish, such as buckets and trash cans, we have no mosquitoes!

Another reader wrote in to say that he thought the same heating-up phenomenon (and we now know, cooling-down phenomenon) would hold true for NFT systems. He thought that with the relatively thin levels of water in the NFT troughs, it was possible that they would also lose and/or gain heat to the point where the system malfunctioned in some way.

Does anyone in the readership have experience with NFT systems? We'd welcome some input from an expert on this one.

We hope this has been useful to you. If you have any additional questions you would like us to answer in this continuing series of Special newsletters, please email them to Tim.

With our Aloha, Tim and Susanne


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Pistou basil growing in our Aquaponic Solar Greenhouse


Large-leaf basil interplanted with tomatoes equals yummy pesto in the future!


Tim joking around, but really showing off the strength of the 20-foot curved beams used in the Aquaponic Solar Greenhouse.

Special Offer! Sign up for our June 28-29 Aquaponic Solar Greenhouse Training and receive our Micro System package for free so you can begin studying aquaponics! ($99.95 value)

More Information on Hawaii Aquaponic Solar Greenhouse Training


Tomatoes on the north wall of the Hawaii Aquaponic Solar Greenhouse; the wall reflects light and provides a built-in tomato trellis


Tim with the PV system charge controller, inverter, breakers, and cabling from the PV panels on the wall to the right. The roll-down white plastic cover (rolled-up in this picture) keeps all this (black) equipment from heating up too much on a sunny day.

"The Fish's View"
(new column!)

We have a bias when sharing information about commercial aquaponics: we are only interested in your success!

If you need to pay the bills with the produce from your aquaponics system as we do, you will want to use equipment and techniques proven to be dependable and productive on a commercial aquaponic farm.

Everything we share is based on our direct experience over the last four and a half years. We built our farm ourselves on a very thin dime, so we've had to be observant and learn our lessons the first time around, with no timeouts or free rides.

Susanne got our aquaponics systems USDA organically certified (we are the first organically certified aquaponic farm in the USA). We shipped an organically certified product to Costco for nearly two years, something no other aquaponic farm has ever done. We've developed ways to make commercial aquaponics more energy efficient, less labor intensive, and more profitable. We are successful at commercial aquaponics.

We think our success is a major reason we've been repeatedly attacked in online forums. As an associate of ours in Trinidad says: "No one throws stones at a tree with no fruit!".

What we teach in our trainings, write in our DIY manuals, and share freely in this newsletter is based on our experiences over the past four and a half years with large-scale commercial aquaponics. We also share peer-reviewed science from recognized journals and publications.

Our point is this: commercial aquaponics is very different from backyard aquaponics. Commercial aquaponics must be profitable, or you are out of business at a loss. There are no such requirements for backyard aquaponics system designs. They can have all kinds of inefficiencies built in, for there is no requirement that they turn a profit.

If you read something in this newsletter about commercial aquaponics, and then an "expert" tells you in an online forum "They're all wrong, those systems don't work, and you can't make money with aquaponics", it may leave you with a valid question. Here's how to resolve it:

First ask for their background and  experience with large-scale commercial aquaponics. A few of the "experts" who say our systems don't work don't even have aquaponics systems, let alone large commercial systems.

Ask how many years they operated a commercial scale aquaponics venture that their income derived from. We'd guess in most cases, the answer from these experts is "none".

The aquaponics community is in a fledgling state, and can truly benefit from all the aquaponics teachers, consultants, and farmers with experience. But the waters are getting muddied by people with little or no experience, just because they have a personal grudge.

Until they get some experience, and have an idea what they're talking about, it would benefit all of us to stop the sniping and open our minds a bit...just a suggestion.

To be very clear:

We are not saying that the backyard aquaponics methods don't work, we are saying that on a large, commercial scale, some of those methods have limitations, and some of those limitations are so severe that they can kill your business.

More on the business of commercial aquaponics next week, with a newsletter about an aquaponic farm that is making money and expanding all the time.

They just happen to be one of our students.

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Honoka'a, Hawaii 96727

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