Aloha Aquaponics



At the University of Hawaii’s College of Tropical Agriculture and Human Resources(CTAHR), research into soilless systems is underway with an aim to decrease Hawaii’s dependence on imports for both food and energy.


With its centuries-old tradition of sustainable food production, Hawaii boasts a long history of close contact with Nature. Early Hawaiian agricultural systems were closely linked to the natural environment to ensure long-term productivity and support to the inhabitants of these Islands.


Today, at the University of Hawaii’s College of Tropical Agriculture and Human Resources (CTAHR) in Honolulu, the island state’s traditional, sustainable agricultural link with the ecological and biological cycles is being continued. For over 100 years, much work has been conducted by CTAHR in its various incarnations and partnerships to develop and improve agricultural technologies relevant to organic growers. This includes intensive cover crop research, promoting the importance of locally grown produce, developing biological and cultural methods for controlling pests without chemicals, and the use of biological nitrogen fixation to significantly increase production of high protein foods while at the same time reducing the need for commercially produced fertilisers.


Working as an aquaculture specialist at CTAHR’s Department of Molecular Biosciences and Bioengineering is Clyde S. Tamaru, PhD. Born and raised in Hawaii, Dr Tamaru received his doctorate from the University of Tokyo, Faculty of Agriculture Department of Fisheries. Dr Tamaru heads CTAHR’s aquaculture extension team, which provides technical assistance in aquaculture and aquaponics to private and public sector stakeholders within the state and abroad. The information and assistance is science based and accomplished by maintaining an active research portfolio that covers Hawaiian fishponds, biofuel byproduct remediation, aquaponics, and developing hatchery technologies for a variety of freshwater and marine species.



In search of food self-sufficiency


The overarching aim of Dr Tamaru’s and his team’s current research and extension efforts is to decrease Hawaii’s dependence on imports for both food and energy.

“The overall goal of CTAHR over the course of the next 10 years is to assist the State into increasing our self-reliance in the production of our own food. Currently, 85% to 90% of our food and more than 90% of our energy is being imported,” Dr Tamaru says.


According to a recent white paper, Food Self-Sufficiency in Hawaii by Dr Tamaru’s colleague, Dr Pingsun Leung, the pressing need for Hawaii is to increase its food self-sufficiency:  Hawai‘i is located approximately 2,506 miles from the continental United States. Most of Hawai‘i’s food is imported, which makes it particularly vulnerable to natural disasters and global events that might disrupt shipping and the food supply.


Hawai‘i has been hard hit by global economic events. Fluctuating oil prices, rising food costs, and the worldwide financial crisis have contributed to a downturn in Hawai‘i’s visitor arrivals, lowered economic forecasts, and rising unemployment. These events highlight the importance of food self-sufficiency and food sustainability priorities for Hawai‘i.


“Currently, our entire agricultural output is approximately US$500 million. By reducing our imports by just 10%, over US$300 million would stay in Hawaii, over 2000 jobs would be saved and our economy – which is highly dependent on the visitor industry – would be diversified,” Dr Tamaru says.


Dr Tamaru points out that the initiative would also offer several other benefits, including a decreased carbon footprint and a reduced risk of introducing invasive species.  “We are focused on just one aspect of the overall effort in becoming more self-reliant in food production and that is in the area of soilless farming,” he says.

“Aquaculture and hydroponics are two soilless farming technologies and the current focus is to develop a third, which is the integration of the two.”


In the highly urbanised town of Mililani at the centre of Hawaii’s Oahu Island, Mari’s Gardens is a nursery that has greenhouses and also integrates Hawaii’s biggest aquaponic farm.



Benefits of aquaponic technology


According to Dr Tamaru, aquaponic technology addresses several limitations that are presented by traditional soil-based agriculture.  “The first is that it is soilless farming and therefore not dependent on having ‘good’ soil or any kind of soil. Aquaponics also allows for the ability to produce food in areas where you would have never thought possible,” he says.  “This situation is particularly acute in an island state where land is a premium resource. In my presentations I use a slide, , which summarises this challenge, where prime agricultural land is set to be developed into a subdivision that will provide over 11,500 homes, schools and new businesses.


“There are no simple answers and it is a situation that will not go away,” Dr Tamaru says.  “The emerging technology of aquaponics allows for expansion of agriculture, using marginal lands and/or novel uses of already developed land.


“Aquaponics also addresses another resource limitation—one that many folks do not seem to realise is coming—and that is fresh water. Mark Twain has been attributed in saying: ‘Whiskey is for drinking but water is for fighting over’,” he says.

“In terms of water, aquaponics is estimated to use only 5% of what it would take to produce the same crop in soil. Things are even more acute when you live on an island surrounded by the ocean and this is another reason why we think it is important to focus on the development of this form of food-producing technology.”



Dr Tamaru also cites a third benefit of aquaponic technology.  “The aquaculture portion of aquaponics addresses the shortcomings of being able to satisfy the demand for fish and fishery products,” he says.  “Aquaponics merges the production of two separate technologies (aquaculture and hydroponics), representing the development of the most productive of food-producing technologies per unit area.

“Aquaponic technology offers sustainability, which rests on the principle that we must meet the needs of the present without compromising the ability of future generations to meet their own needs,” Dr Tamaru says.


“Therefore, stewardship of both natural and human resources is of prime importance. The three Rs (reduce, reuse, recycle), which define sustainability, are embodied in aquaponics but not necessarily when aquaculture or hydroponics are practised separately.”




Ongoing research


Small aquaponic systems allow people to grow plants and fish in their backyard, but Dr Tamaru wants to see more growth in commercial aquaponics.  “However, we don’t want to compete against good agriculture land. We want places that are marginal or not even used,” he says.  As an emerging technology, there still is no one formula for commercial aquaponics systems in Hawaii, says Dr Tamaru.

“Likewise, for urban gardeners where system and systems designs are as varied as the folks who are setting up and running their own systems.”


Dr Tamaru explains that in aquaponics, the waste from the fish – including ammonia and nitrate – helps fertilise the plants; then the water is purified before being recirculated back to the fish tank.  But not just any fish can be raised in these tanks,” Dr Tamaru says.  “Tilapia is the main fish used in Hawaii, because they can tolerate these levels of ammonia and nitrate.”  Most tilapia now sold in Hawaii supermarkets and restaurants are imported, but Dr Tamaru wants to see more local-grown sales.

Dr Tamaru has found that setting up and maintaining a successful aquaponic operation has often involved a trial and error approach.


“We have had to take a step back and focus on answering some of the most basic of questions, for example, what kind of feed do I use in my aquaponic system,” he says.

“Basically, it depends – you need to look at what kind of fish and what kind of plant you plan to produce.  “My current research shows the impacts of two kinds of fish feed (Rangen with low protein, low fat; and Silver Cup with high protein, high fat) on the growth of tilapia and three kinds of leafy greens,” Dr Tamaru says.


“When tilapia were fed the two different types of feed, the high protein, high fat diet resulted in superior growth of the fish. However, there were no differences observed when growing lettuce when using either source of fish effluent. What we did find, however, was that there were significant differences when growing kai choi [Brassica juncea]. So the answer as to what type of fish feed you should use in an aquaponic setting will depend on what type of plant.”


In terms of pH used in the aquaponic systems, Dr Tamaru says that using Chinese taro plants in three different solid media and in an ebb and flow aquaponic systems showed that pH remediation is more important in producing larger leaves than the solid media used in growing the plants.  “We are currently investigating which strategy of pH remediation is the most effective from the standpoint of plant crop outputs, delivery systems, micro-nutrient supplementation, etc,” he says.



Challenges and opportunities


Dr Tamaru says that one of the major difficulties encountered in setting up and maintaining an aquaponic operation is the start-up cost.  “This can prove a major challenge, particularly for aquaponic producers at a commercial scale,” he says.

“Local market demand for home-grown products must increase for local farms to remain viable. There is a definite need for research and extension work to demonstrate that purchasing locally grown products is beneficial and that they can command higher prices.


“For commercial aquaponic producers one of the main challenges facing them is dealing with pests (for example, aphids, downy mildew, mites, rose beetles and the like). This is especially true if they want to be organically certified, as the number of pesticides and their effectiveness are limited,” he says.  Looking to the future, Dr Tamaru says that there is still much to undertake.  “We have a lot of work, both basic and applied, that needs to be done on the nitrification process, microbes involved, controlling efficiency, plant quality, fish species, plant species, system design, food safety, and so on. The quantity and quality of the plant produced aquaponically becomes very important, especially if there are differences that distinguishes it from hydroponically or terrestrially produced,” he explains.


“We are also seeing differences in protein content, antioxidants, micronutrients that indicate the aquaponic technology results in a higher quality plant. These kinds of results need to be demonstrated and validated and make up a large part of our future work.”



Mari’s Gardens aquaponic venture


Dr Tamaru and his team’s work in aquaponics is linked with the successful transfer of those technologies to appropriate end users. One such case is Mari’s Gardens in the highly urbanised town of Mililani at the centre of Hawaii’s Oahu Island.


Originally set up as a commercial nursery, Mari’s Gardens has evolved over time and has now dedicated one of its 18 acres to aquaponics, making it Hawaii’s biggest aquaponic farm and one of the pioneers in the commercial use of aquaponics on a large scale.At Mari’s Gardens aquaponic facility there are five tanks with 2500 to 3000 fish in each.  Owner Fred Lau says he reuses water from his nursery to produce 150 pounds of cucumbers a day and 14,000 heads of lettuce a month, using five tanks with 2500 to 3000 fish in each. Around 200 pounds of fish a week are also produced.



Mari’s Gardens owner Fred Lau says he reuses water from his nursery to produce around 14,000 heads of lettuce a month.  “It is a sustainable method of farming, but economically, it could take a while to be beneficial,” Mr Lau says. “The start-up costs can be quite expensive.”  Since the first planting in February 2010, Mari’s Gardens has become the largest aquaponic producer of Manoa lettuce in Hawaii.  “We can’t grow it fast enough,” says Fred Lau.  “Our produce includes Manoa lettuce, Green Oak Leaf, Red Oak Leaf, Green Onions, Japanese cucumbers, tomatoes, and beets.

“Amidst expansion, we are testing other crops as well. Our produce is certified organic so no synthetic pesticides or fertilisers are used in the production process. We are also Food Safety Certified,” he says.


Along with the diversification of plant products is the expansion and diversification of the fish crops with the recent establishment of a Chinese catfish hatchery.

“Staff receive training from our aquaculture extension faculty in the induction of spawning and the artificial fertilisation of ovulated eggs. Currently, we are in the process of rearing the thousands of larvae that were produced,” Mr Lau says.


“This effort will lead to becoming self-reliant in producing seed for further expansion of our Chinese catfish enterprise.”  Tours of the aquaponic facility are available where an in-depth explanation of how aquaponic systems work is given as well as a talk on why the system is the most sustainable method of farming possible. Fees from the tours are used to help perpetuate ongoing research and development of aquaponics.


Tours of Mari’s Gardens are available where an in-depth explanation of how aquaponic systems work is given as well as a talk on why the system is the most sustainable method of farming possible.  Like Dr Tamaru, Fred Lau believes that aquaponics is more than a just commercial venture.  “The basic principles of aquaponics allow you to tailor it to just about any situation or environment and, with decreasing available land, that’s very important,” he says.  “In terms of being an efficient and sustainable food-producing technology, it’s the way of the future.”



For more information about the College of Tropical Agriculture and Human Resources (CTAHR) at:


More information about Mari’s Gardens at:



Written by Christine Brown-Paul

Reproduced from Practical Hydropnics & Greenhouses

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