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Here is the latest installment in my monthly series for Growing Edge.com
This article continues a monthly series about aquaponics and all the components you need to build your own a thriving aquaponics system. This month we will talk about fish tanks and grow beds, and the optimal size ratio between the two.
Sizing your fish tank defines the ultimate size and flexibility of your aquaponics system, so consider the size early in your design process. If you are building a small, desktop system using an aquarium, you will be restricted to aquarium fish that will live comfortably in the size aquarium you own. If you want to grow larger, edible fish, the most important rule-of-thumb when choosing a tank is to make sure it is made of sturdy, food grade or food safe materials. Next, make sure that the tank is at least 18” deep (457mm), and holds at least 50 gallons (189 Liters) of water. Tanks need to hold approximately 50 gallons (189 Liters) or more in order to grow “plate sized” fish (12” and 1 ½ lbs, 300mm and 680g).
Aquaponics fish tanks can be made from just about any structure that fits the right dimensions and is lined with EPDM pond liner.
You can also use everything from recycled bathtubs, stock tanks, and IBC tanks, to recycled barrels. Our 60 gallon Aquabundance Fish Tank has been specifically designed for aquaponic fish growing, so you might want to check it out as well.
Since your fish tank will be difficult to move once filled, you should carefully consider where you place it. Ideally the fish tank should be located indoors or outdoors in the shade. Fish don’t require sunlight to thrive and the extra heat and algae growth from sunlight could become a problem. Also, be sure the tank is on a solid surface that can handle the weight of the tank when filled with water. At 8.3 pounds per gallon, you will very reach a weight that might exceed the structural limits of the surface you are planning to use.
Wherever you choose to set up your tank, you will be well served to at least partially cover it to help prevent debris, children, and pets from falling in. Covering it will also lower the amount of light reaching the tank. This will help you keep control of the tank’s temperature and reduce algae.
Fish tank volume governs the maximize size of your grow bed. Here is why. The plants need the fish waste to thrive. The bigger the grow bed and thus the more plants, the more fish waste required. Simple – you need enough fish to support your plants. In general the recommended grow bed to fish tank ratio is approximately 1:1, i.e. the fish tank volume should be approximately equal to the volume of the grow bed. This ratio can also be thought of in gallons per cubic foot, striving for 6 gallons (22 liters) of fish tank to every cubic foot of grow bed. For example, a 50 gallon (189 liter) tank would be able to support 6 to 8 cubic feet of grow bed. You can extend this rule of thumb all the way to 2:1 (twice the fish tank volume to grow bed volume) but be sure to reduce the stocking density of your fish tank accordingly as this approach reduces your ability to filter the fish tank water with the grow bed plants.
(next I talked about Grow Bed Depth, which was pretty much a shortened version of last week’s post Aquaponics Grow Bed Depth, so I won’t repeat it here)
Do not use metal containers, not even galvanized metal, for either the grow bed or the fish tank. Metals can quickly corrode, throwing your system off-balance by lowering your tank’s pH. Metal containers may also leach undesirable chemicals into your system. Copper and zinc are particularly dangerous for fish. An excellent choice is the AquaBundance Aquaponics Grow Bed, which is the only grow bed on the market today that has been designed with the aquaponic gardener in mind.
The remainder of the articles in this series will be centered on creating and successfully operating, a home media-based system. The next article will be about plumbing and the water flow between the tank and the bed, followed by articles about fish and plants. Please comment with your questions and thoughts!
How deep should your aquaponics grow bed be? Grow bed depth in a media based aquaponics system is a subject not without a little controversy. The majority of media-based aquaponic growers will say that you should have about 12” (300 mm) of media, with the top 1 – 2” being left dry to reduce algae and fungal growth. There are those, however, who claim to be growing successfully in substantially less than that.
Deeper beds are more expensive because of the cost of the extra media, the cost of supporting the weight of the extra media and the need for a larger fish tank to fertigate all that media. Plus, if you stick to a 4 – 6” depth you can use standard hydroponic flood and drain trays which are widely available.
Here is why you don’t want to do that.
If you pay close attention you will notice that everyone who touts shallow grow beds expresses one or more of the following limitations
- Limitations on the types of plants you can grow – shallow beds work great for shallow rooted and/or short lived plants such as lettuces and greens, but won’t work for longer lived, deeply rooted plants such as indeterminate tomatoes, cucumbers, corn, melons, etc. This is both because shallow beds don’t provide the base of nutrients and bacteria required for the relatively long life of these plants nor do they provide the space for large root zones. Travis Hughey, Murray Hallam, Joel Malcom (and I) all talk about the almost limitless variety of what you can grow in media based aquaponics. This is because we are all using beds about 12” deep.
- “Dead zones” and the need to clean out your beds – As the illustration below shows, in deep beds a layered eco-system establishes that prevents the development of “dead zones” (anaerobic areas) in your bed. Because of the thriving environment flush with beneficial bacteria and worms and plenty of space for the roots to grow, you never need to clean out your grow bed – they, along with the plants, do the cleaning for you. When there is enough room for a robust eco-system to establish itself, all the elements of that system thrive and become self-sustaining. That happens at about 12” of media depth.
Here is an excellent explanation of what happens in the grow beds excerpted with permission from Murray Hallam’s new Aquaponics Secrets video:
Surface or dry zone (Zone 1) – The first 2” (50mm) is the light penetration and dry zone. Evaporation from the bed is minimized by the existence of a dry zone. This dry zone also protects the plant base against collar rot. Additionally, by ensuring that this zone is kept dry, algae is prevented from forming on the surface of the grow bed media and moisture related plant diseases such as powdery mildew are minimized.
Root zone (Zone 2) – Most root growth and plant activity will occur in the next zone of approximately 6” – 8” (150 – 200mm). In this zone, during the drain part of the flood and drain cycle, the water drains away completely, allowing for excellent and very efficient delivery of oxygen rich air to the roots, beneficial bacteria, soil microbes, and the resident earth/composting worms.
During the flood part of the cycle, the incoming water distributes moisture, nutrients and incoming solid fish waste particles throughout the growing zone. The worm population does most of its very important work in this zone, breaking down and reducing solid matter and thereby releasing nutrients and minerals to the system. “Worm Tea”, as it is commonly known, will be evenly mixed and distributed during each flood and drain cycle. “Worm Tea” and the fish are entirely compatible.
Solid collection and Mineralization Zone (Zone 3) – This is the bottom 2” (50 mm) of the grow bed. In this zone fish waste solids and worm castings are finally collected.
The solid material has been reduced by up to 60% by volume, by the action of the resident garden/composting worms, and microbial action. During each flood and drain cycle, what is left of the solids percolates down into this zone. Further and final mineralization occurs in this area via bacterial and earth worm activity. Due to the excellent action of the flood and drain cycle, this bottom area is kept “fresh” and vital by the excellent delivery of oxygen rich water during the flood cycle.
I can’t resist putting in a plug for our AquaBundance Aquaponics Grow Bed, which has been designed with all these principals in mind. It is about 12” deep, with an inside lip at the base of the Dry Zone, and features 7.5 cubic feet of growing area. It is made of ¼” thick food-grade PE plastic and has been designed with enough strength so it will never bow out on the sides. It includes a gravel guard that has space for either flood and drain fittings or a siphon (purchase separately). It is very attractive and comes in 4 color choices. Check it out here and let me know what you think!
Last week a Hawaiian aquaponics company that specializes in DIY, raft-based systems sent out a newsletter that had a link to an article that ended with “THESE SYSTEMS DO NOT WORK FOR GROWING MARIJUANA”. The evidence they used was a report from one of their hydroponic- growing students that tried unsuccessfully to grow marijuana using aquaponics.
This started me thinking about a few things. First, because medical marijuana is legal with a permit in Colorado, it is an unavoidable topic of conversation here. I admit I have a tremendous curiosity about how well marijuana would grow in an aquaponics system, especially since every other plant I’ve encountered grows so vigorously. No, I don’t use marijuana nor have I ever grown it, but I have no judgment about those who do. I think that many are doing tremendous humanitarian work with medical patients and marijuana. Plus, who am I to say that my Friday Happy Hour martini is any worse than someone else’s joint? But my real curiosity is with the plant itself…
I think that the statement above about the plant not growing in “these systems” may be true. But this is because the referenced system is raft based. I have become convinced from my experience, conversations, and research that raft based systems, while absolutely the best for commercial operations growing lettuces, greens and herbs, don’t offer the robust nutrient mix that a mature media based system offers.
Think about it. The engine of an aquaponics system is what I have started calling “the conversion team” of beneficial nitrifying bacteria and composting red worms. The bacteria convert the main, liquid source of
waste from the fish into food for the plants and reside on all moist surfaces of an aquaponics system. Which system has more surface area –a raft-based system where bacteria reside on the underside of the raft itself, as well as the sidewalls and the plumbing, or in a media-based system with sidewalls, plumbing, and 12” of gravel or Hydroton? My vote is for the media based system.
Then you have the solid waste, which provide additional micro and macro nutrients for the plants. In raft-based systems, the solids are filtered out and removed as unwanted waste. In media-based systems, the solids remain in the grow bed and are digested by composting red worms that return it to the system ecology as incredibly nutritious vermicompost.
Adding further fuel to my conviction that there just isn’t anything that can’t be grown in a mature media-based aquaponics system, I recently had the delightful pleasure of interviewing Travis Hughey. He is the inventor of the Barrel-ponics™ system and the father of that movement in the U.S. I interviewed him for an article I’m writing for BackYard Aquaponics Magazine. While we never discussed marijuana specifically, Travis agrees that he has yet to find the plant that won’t grow well in media-based aquaponics. As evidence here are some photos of his current aquaponic gardens, along with some of my own.
So can marijuana be grown in aquaponics? I sure don’t see why not. While it is a very special and
obviously controversial plant, it is still just a plant. I’m willing to bet that there are people out there who are trying to grow marijuana using aquaponics and probably succeeding mightily.
Let me know what you think.
A couple weeks ago I started a monthly series on Aquaponics in one of my favorite online gardening magazines – Growing Edge. The intent is to cover a wide range of topics about aquaponics how-to, and the plan is to share them in this blog with you as well. This first article serves as an introduction to aquaponics and explains some of the benefits of aquaponic gardening. It also talks about the types of systems people are using today. I hope you find it useful, and perhaps worthy of passing on to friends and family who might also be cultivating an interest in aquaponics.
This is the first article in a series that will focus in detail on all the components of a thriving aquaponics system, from the fish, plants and bacteria to the grow beds, fish tanks and plumbing options. We will also talk about worms as the secret weapon of media-based aquaponics as well as the different fish feed options that are available. Hopefully by the end of the series (and who knows when that will be) I will have convinced some of you that aquaponics should be at least a part of your growing repertoire.
It seems appropriate that we start our journey together by answering the question: What is aquaponics? At its most basic level aquaponics is the marriage of aquaculture (raising fish) and hydroponics (growing plants in water and without soil) together in one integrated system. The fish waste provides organic food for the growing plants and the plants naturally filter the water in which the fish live. The third and fourth critical, yet invisible actors in the play are the beneficial bacteria and composting red worms. Think of them as the Conversion Team. The beneficial bacteria exist on every moist surface of your aquaponic system. They convert the ammonia from the fish waste that is toxic to the fish and useless to the plants, first into nitrites and then into nitrates. The nitrates are relatively harmless to the fish and most importantly, they are great plant food. At the same time, the worms convert the solid waste and decaying plant matter in your aquaponic system into vermicompost.
Here is the rest of the story
- Aquaponic Gardening enables home fish farming. You can now feel good about eating fish again.
- Aquaponic Gardening uses 90% less water than soil-based gardening.
- Aquaponic Gardening is four to six times more productive on a square foot basis as soil-based gardening. This is because with aquaponic gardening, you can pack plants about twice as densely as you can in soil and the plants grow two to three times as fast as they do in soil.
- Aquaponic Gardening is free from weeds, watering and fertilizing concerns, and because it is done at waist height there is no back strain.
- Aquaponic Gardening is necessarily organic. Natural fish waste provides all the food the plants need. Pesticides would be harmful to the fish so they are never used. Hormones, antibiotics, and other fish additives would be harmful to the plants so they also are never used. And the result is every bit as flavorful as soil-based organic produce, with the added benefit of fresh fish for a safe, healthy source of protein.
- And if you are already a hydroponic gardener switching over to Aquaponic Gardening you can enjoy the following advantages
- Aquaponics has been shown to be more productive than hydroponics after the aquaponic bio-filter is fully established. (study by Dr. Nick Savidov, of the Crop Diversification Center South, Alberta Agriculture Food and Rural Development at Brooks, Alberta, Canada report in the “Aquaponics Journal,” 2nd Quarter, 2005)
- EC (electrical conductivity) tracking is replaced by tracking of Ammonia, Nitrite and Nitrate. Once your system is fully cycled you will only need to measure these about once a month or so vs. the much more frequent tracking of EC.
- pH is much more stable, again once your system is fully cycled.
- Fish feed is significantly less expensive than hydroponic nutrients.
- You never dump out your nutrient solution! Rather than having problems with chemical imbalance that you regularly experience in hydroponics, in an aquaponic system you are achieving a natural nitrogen balance that is the hallmark of a balanced eco-system. I view the water in my system as a critical component that I have nurtured into the near perfect balance at which it stays for as long as I choose to run my system (in my case…years).
- Best of all, you can say goodbye to pythium forever. It is non-existent in aquaponics.
Types of systems
Aquaponic systems can be created using a variety of hydroponic techniques, although systems that run-to-waste are not considered true aquaponics because they don’t close the loop by returning filtered water back to the fish tank. The most prevalent aquaponic growing methods are Deep Water Culture or raft-based, and Flood and Drain, or media-based. NFT and aeroponic techniques have also been used, but less widely and with limited success because solids from the fish waste – no matter how filtered – will eventually clog up the smaller tubing used by these system types.
Deep Water Culture (DWC) is where most of the university research on aquaponics has focused. This is especially true at the University of the Virgin Islands where Dr. James Rackocy has spent the past 30 years perfecting this growing technique. In DWC the fish are held in tanks separate from the plants. The solid fish waste is removed from the water using a settling tank and clarifying filters before it is sent on to the plant raceways. This prevents the plant roots from becoming coated with solid matter and suffocating. The fish water then circulates through a raceway that is covered with floating rafts. These rafts have holes in them to accept planted net pots whose roots dangle directly into the water. Newly planted rafts are dropped into the beginning of the raceway. The rafts progress along the raceway with each newly planted raft pushing the older rafts to the end of the raceway where they are pulled from the water and harvested. DWC is an excellent aquaponic growing technique for commercial growers because it is relatively easy to plant, tend, and harvest a large number of fast growing plants such as lettuces and some herbs. DWC also provides very stable water temperatures and pH levels because of the high volume of water required. The downsides of DWC are that in filtering the solids you lose many of the micro-organisms required to grow healthy, larger, fruiting plants. Also, while it has been done, it is difficult to grow larger plants to full size because of the challenges of getting enough oxygen to the larger root zone of a plant that lives its entire life in the water.
Most aquaponic home gardeners are using media based, flood and drain systems. A media based grow bed optimally has about 12” of either ½ – ¾” gravel (no limestone or granite!) or expanded clay (Hydroton). The reason for these extra deep beds is to enable a multi-layered environment that supports enough beneficial bacteria and composting red-worms to maintain a very stable bio-filter for your fish. It also gives you ultimate flexibility in what plant types you grow because you don’t ever have to think about the size of your root mass. Some gardeners are even growing subterranean plants, such as potatoes and carrots.
Most media-based grow systems use a timer to turn the pump in the fish tank on and off (some use a system
based on a siphon but how those work will have to wait for another article). A typical timer cycle is 15 minutes on followed by 30 – 45 minutes off and then the cycle repeats. When the pump starts, water from the fish tank is pumped into the grow bed. The grow bed fills with water up to about 10” or so. Obviously, this provides plenty of water and nutrients for the plants. Hydroton or other media above this height are in the “dry zone” and stay dry all of the time. When the water reaches about 10”, any additional water immediately returns to the fish tank through an “overflow” mechanism. The returning water strikes the water surface in the fish tank; thereby creating turbulence which helps aerate the fish tank water. When the timer turns off, the pump stops and the rest of the water in the grow bed returns to the fish tank. This period of inactivity gives the roots a chance to dry out and “breath” the air – something they greatly appreciate. Then, when the timer triggers the pump again the cycle repeats.
The remainder of the articles in this series will be centered on creating and successfully operating, a home media-based system. I will be approaching this sequentially as if you were building your own system and needed to know what to do first, then second, etc. (although you might want to consider purchasing an aquaponics system kit that has been manufactured for optimal performance, such as our Aquabundance System!) The next article will be about how to source a grow bed and fish tank, how to think about the ratio between the volume of these two pieces, what to consider in locating them, etc. We will then discuss plumbing and the water flow between the tank and the bed, followed by an entire article about fish. We have much to talk about!
At the LOHAS Forum (Lifestyles of Health and Sustainability) a couple weeks ago, we were struck by the wide variety of people that we met. We met CEOs, or former CEOs, of Aveda and Horizon Dairy. We met a man who believed that a particular kind of clock could set your bio-rhythms. We met Huffington Post columnists and activists for a wide range of causes. We met bloggers and book authors. What brought them all together for those few days in Boulder was their fierce commitment to the notion of sustainability.
While I was attending one of the sessions my husband struck up a conversation with the producer of the film “Fuel”. The producer left the conversation pondering the possibility of aquaponics, and us, somehow being involved in his next film project but not without first asking if he could take one of our Aquaponics Explained videos in exchange for a copy of “Fuel”. Not wanting to seem rude, and spotting a possible PR opportunity, my husband agreed to the exchange. Last weekend we decided to watch “Fuel”, although with a skeptical pre-disposition. Here is a trailer:
It was excellent. Viewed from the perspective of one man’s obsessive quest to popularize bio-fuels, Fuel takes you on a roller coaster ride up the rise of vegetable oil-based bio-fuels, (spoiler alert!) and then back down as you realize how much fuel is used to power corn production in this country. When we use as much energy to create bio-fuel through fertilizers, pesticides, processing and transport as we can extract from the resulting product; we stretch to beyond the breaking point the notion of sustainability. Anyone who read Michael Pollen’s Omnivores Dilemma, or seen Food Inc. or King Corn knows this.
The good news is that the film ends on a high note with the emergence of algae farms. Algae are a fast growing powerhouse of bio-fuel potential and the best part is that algae can be grown in waste water. This is the part in the movie where I jumped up and said “just like aquaponics!”
This experience got me thinking. My slightly blasé attitude through most of the movie was transformed at the notion of converting waste. I realized that there are several levels within the notion of “sustainability”. I think the deepest of these come from technologies that transform waste bi-products into substitutes for depleted or endangered resources. This is where it gets exciting, and this is why using algae grown in waste water runoff from utility companies caused me to jump from the couch. I felt the same way when I had dinner a few years ago with a vermicomposting expert who was working to set up worm farms at cattle feed lots to create organic fertilizer from the toxic sludge that is the scourge of those operations.
And, of course, this is just one of the many reasons why I get so excited about aquaponics. The waste bi-products of fish farming operations and home aquariums, are – if converted to an aquaponics setting, -naturally converted into organic fertilizer for plants. This eliminates the need for hydroponic nutrients that unfortunately leave behind a toxic mix that must be disposed of accordingly. And the plants are now a natural filter for the water, eliminating the need for mechanical filtration. It solves key waste disposal problems in both industries (aquaculture and hydroponics) and hands each a benefit in return, i.e. purified water and a complete, organic fertilizer.
Now if only we could figure out how to produce a benefit from the Gulf oil spill…
Last week a professional photographer came over to take product shots of our new AquaBundance system. Since it was a bit of a drive for him he and his wife decided to make a day of it and brought their young son. He was of course instantly drawn to the fish, and as he peered into the tank he exclaimed “look at all the babies!” “Impossible” I thought. “I have all male tilapia stock”. But I humored him by looking into the tank myself. I’ll be damned. Floating on the surface of the tank was a miniature school of about 30 tiny fish. Those boys had babies! Here is a quick video of the babies, and our new aquaponics nursery set-up for housing them.
As background, most tilapia that are raised in this country are male because males grow bigger, faster, and reproduction is just plain messy, no matter what the species. Babies lead to fighting, territorialism and the tank quickly gets over populated.
There are primarily two methods in use in the U.S. today to insure all male tilapia stock.
The first, most frequently used method is called Direct Hormonal Sex Reversal. Basically the young fry boys and girls are flooded with male hormones at an early age causing them to all grow up to be boys. The second method, and the one I find more palatable, is called Genetically Male Tilapia (GMT). Basically a Super Male is produced with YY chromosomes (i.e. two male chromosomes) so when he reproduces he can only produce another super male or a male. Hopefully this wonderful graphic from FishGen.com, will help explain what is going on. They also have a much more detailed explanation of how all this works on their website – just click on the image to go there.
Last December I got 100 “all male” tilapia that had been sexed using GMT, but since the inventors claim that the process is “95% effective” I guess I shouldn’t be surprised that a few girls slipped in. For now I’m enjoying the babies and the fact that Mother Nature always seems to find her way around our efforts to thwart her.
I adore Murray Hallam. His charming demeanor on his videos reminds me of my father with an Australian accent. I also greatly respect the work he has done in home aquaponics in Australia. He is one of two men who have largely been responsible for the boom in the market down there. We tend to agree about just about everything when it
comes to media based aquaponic gardening. I recently told him that I think our only point of departure is that I’m a very big fan of expanded clay pebbles (Hydroton) as a growing media because it is lightweight and is very easy on my hands. Murray feels that those concerns are mainly for women (those Aussies are just tougher than we are). A very minor philosophical departure indeed! His systems are well thought out and well made. His email newsletters are informative and amusing. His videos are an outstanding blend of garden-geek dramatic theater and practical how-to.
So you can imagine how excited I was when Murray approached me earlier this year about not only becoming a reseller of his videos in the U.S. but also sponsoring one of two stops in the U.S. for his first ever tour here. What an incredible opportunity to get to spend time learning directly from the master himself!
My partner in the event is the Denver Botanic Gardens, and the workshop will be from 9:00 a.m. to 3:00 p.m. Sunday, September 19th at the Denver Botanic Gardens. Space is very limited (we have a smaller room than I originally hoped for) so I recommend signing up early. Click here for more information.
Also, if you are interested in gathering with some fellow aquapons in Boulder the day before (Saturday) I’m considering hosting a tour of several aquaponics setups around this area – just let me know by commenting on this post so I can keep you in the planning loop.
Hope to see you all there!