Is it possible to set up a saltwater aquaponics system to grow vegetables? I’ve never seen or heard of such an installation but the topic is occasionally raised among those new to aquaponics. An honest query really considering saltwater shrimp, shellfish and/or fish such as red drum are valuable and sought-after livestock.
Taking this a step further, saltwater aquaponic installations would look a lot cooler when you have damsels, tangs, butterfly, rays and sharks swimming around vs freshwater species which look rather dull in comparison.
Aquaponics can only use freshwater, right?
I’m guessing most aquaponic farmers believe as I, salt water would kill most vegetables. Given this accepted tenet, we’d therefore use only fresh water and freshwater fish such as tilapia, bluegill, trout, perch or catfish. However, let’s consider the potential of using saltwater given more than 70 percent of the world is covered in it! This would definitely boost overall food production on the coasts where most of the population lives.
Vegetables tolerant of saltwater
To my surprise, there are plenty of vegetables tolerant of salt water. Following is a post about salt-resistant crops: http://blogs.ifas.ufl.edu/pinellasco/2014/03/28/salt-tolerant-vegetable-gardening/ Here is another article exploring the same:
This article is about a Dutch farmer looking to grow potatoes using saltwater: http://www.micronesiaforum.org/index.php?p=/discussion/13710/fruits-and-vegetables-grown-in-saltwater-could-help-solve-world-food-shortage
Saltwater aquaponics for purely saltwater crops
So let’s take this even a step further. Rather than building and experimenting with growing traditional vegetable crops in saltwater, why not grow saltwater aquatic plants with commercial value in these systems. Seaweed is a great example and here’s an article about growing this crop using aquaponic methods: http://aquaponicsjournal.com/docs/articles/Seaweed-is-Common-Denominator.pdf
More on saltwater aquaponics at this wikipedia page: https://en.wikipedia.org/wiki/Saltwater_aquaponics
Now that our patio aquaponics system is well into cycling after the introduction of tilapia, we are ready to plant our first seeds in the grow bed. As you may recall, cycling is the process of building beneficial bacteria in the system in order to efficiently convert fish waste into nitrates and nitrites, which our plants will eventually use as fertilizer. It’s time to add those plants — if not, nitrate levels could reach a toxic level which could kill the fish.
Heirloom organic seeds
We’re exclusively using heirloom organic seeds so we purchased our first batch of romaine lettuce from Annie’s Heirloom Seeds. Annie’s ships their seeds in standard USPS and are packaged in branded packets. We were a little disappointed in the number of seeds for the money you pay ($2-3 per packet, with $7 shipping charge) so we’ll explore other sources to see if there is a better value for farming on a small scale.
We understand these seeds are better quality than what you’d purchase at the local big box store, but I think you still need to match volume since those seeds are only $1-2. Plus, we’re starting to see a lot of branded seeds options on the market (think Martha Stewart), that are not heirloom, nor GMO-free but get into the $2-3 price point as well — and those packets are loaded.
Use of rock wool
Some aquaponic farmers throw seed right into the hydroton pebbles but we prefer to set them in rock wool, then place these cubes in hydroton. Although we’d space these wider in a large outdoor system, we’re unsure of how much we could squeeze in our system. For this planting, we’ll space them about three inches apart.
As they grow under artificial light, we could easily lift the rock wool out of the hydroton to re-space. This is the primary reason why I choose to set in rock wool first. We’ll do our best to space as tightly as possible without sacrificing plant quality by stunting growth.
Seeds germinated after two-three days and are growing vigorously. Although we have not hit the recommended 30 days for a tank to completely cycle, we suspect there is enough fertilizer in the system judging from the vigorous growth of the seedlings. I’d consider our first planting in the patio aquaponic system a success.
We plan on planting arugula, bok choy, escarole, water cress, mustard and basil in the future.
Many growers choose tilapia for aquaponics installations. Adding fish is the next step after completing construction of our patio aquaponics system and tilapia is a sensible choice. But where does one source tilapia in Jacksonville, Florida?
Small aquaponics installation, means fewer fish
Since the tank is only 55 gallons, we didn’t need many fish to start cycling the tank. The other consideration is when the tilapia hit a pound, pound and half in weight, we would begin to harvest (eat) the batch and 20 fish full-grown should not overload the tank. Also, since they would be mature, the strong of the 20 would start spawning fry for the next batch of fish. We’d spare the breeders to produce fry in the future.
Blue Tilapia or Oreochromis aureus is our go-to fish
There are many varieties of tilapia. The specific tilapia breed we selected are blue tilapia,Oreochromis aureus. The reason is two fold. Blue tilapia can survive temps that dip into the 50s, so these fish would be hearty enough for an install on the patio in Jacksonville, FL. Yes, temps even in Jacksonville dip into the 30s during the winter but we’ve installed a heater in the tank set at 65 which should kick in during those cold evenings. The other reason for blue tilapia is you are only allowed to have this specific tilapia species for installs in Duval County.
We searched the Internet for a local provider of fingerling tilapia and found Tilapia Depot in St. Augustine. I emailed a couple of times with no response and finally called. I mentioned it wasn’t a big install and needed about 20. Despite the fact it’s just 30 minutes down the road, he suggested he still ship them for an additional dollar each. Really? We finally agreed to hand over $25 in cash if we met him at a convenient time.
Detail of Purchase
In honor of the proprietor’s request, we won’t describe his setup of his business. We were just thankful for him to honor our small purchase and pick up locally. He selected and bagged the 20 fingerlings and threw in a half pound of food as part of the purchase. This is a great practice considering this starter food would be more than enough to grow out each tilapia to about 3-4 inches!
All the fry looked very vigorous and healthy with some being larger than an inch — up to two inches. He packed them in a square foam container and mentioned how, if he were shipping north, he’d throw a heat pack under the bag of water containing the fry and which should last at least 24 hours. Well, we only had 30 minutes back to our home so no heat pack needed.
Introducing Tilapia to Aquaponics Fish tank
Prior to opening the bag, we placed it in the tank in order for the fry to adjust to the tank’s water temperature. After about 5 minutes, we began adding tank water into the bag itself. We continued adding water for another three intervals at five minutes between. We finally released the fish into the tank including the water in the bag. Normally, this is not good practice but since the water in the tank is fresh from tap (added Aquasafe to eliminate Chlorine), there is no beneficial bacteria to begin tank cycling, so the water from Tilapia Depot’s tank would supply this initial bacteria.
Prior to startup of adding vegetables to this install, we need to ensure beneficial bacteria would multiply and be able to produce the nitrates to serve as fertilizer — this would take 30 days of continually feeding the fish with the pump running this water through the system. Bacteria should start growing and multiplying on the hydroton which serve as the media for the vegetables to be planted.
We grow vegetables using exclusively heirloom organic seed. Why? The quality of seed matters because you’ll be eating the fruit these seeds bear. We prefer non-GMO (genetically modified organism) seeds and you’ll find most, if not all heirlooms, are GMO free. However, this is not the only reason we prefer heirlooms.
What are heirloom vegetables?
Heirlooms are vegetables that are more than 50 years old and open pollinated. This is a very good thing. Farmers love raising heirloom because they’re resistant to many pests and diseases, highly marketable and taste great.
Heirloom vegetables grown in Aquaponics
Although we now use only aquaponic methods, we’ve grown heirloom vegetables using traditional methods such as growing in raised beds with compost. We can attest vegetables grown this organic way taste fantastic. Also understand, because the vegetable was in the backyard, fruit can ripen on the vine and harvested at peak. No doubt this adds greatly to the flavorful experience.
Given this high taste baseline, we can confidently claim heirloom vegetables grown using aquaponics taste even better. Tomatoes, peppers, basil and other leafy greens seem to have the biggest flavor boost using aquaponics, judging from our daily (unscientific) taste tests. The best way I could describe the difference in flavor are vegetables taste more “extreme.” A carrot tasted more “carroty,” or a “beet” more “beety.”
More useful information about heirloom organic seeds
Following is a useful article we found on seed sources we used it to start our research to find sources for GMO-free, heirloom seeds.
Internet search for “heirloom organic seed”
Following are seed companies referenced in the article and found in search using “heirloom organic seed” as keywords. We will purchase from several of these sources and provide updates on the results.
Having no yard to grow our own vegetables living in an apartment, it was tough to accept having to buy vegetables at the market. Therefore, we committed to building a small-scale aquaponics installation around a 55-gallon tank destined for our patio. Small-scale aquaponics systems you can buy online will not satisfy our needs. They are either too small to grow a substantial amount of food or pragmatic DIY constructions lacking aesthetics. We didn’t want to add that motley collection. We wanted it to be presentable as well as durable.
Good Aesthetics Starts with Wood Selection
With these considerations, we opted to use select pine appearance boards which are smooth to the touch and are easy to work. The pine serves as both the framework around the tank and material for the grow bed. To match other outdoor furniture, we stained all the pine with blue Minwax water based wood stain and coated it with Minwax polycrylic finish. Construction of the tank framework and grow bed only took about six hours. What took lots of time was applying the stain and finish. This process lasted a week to apply several coats of stain, finish and waited for each application to dry.
Small-Scale Aquaponics System Construction
Rather than use water proof paint in the grow bed, we used 6 mil vizqueen as liner. The liner could easily be replaced when necessary without having to worry about water leaks or seepage into the wood. We drilled a hole in the middle of the grow bed to install a bell siphon, a truly amazing, yet simple technology critical for flood and drain aquaponic systems.
The bell siphon is constructed using PVC reducers combining a 3 in. x 2 in. PVC reducing coupling to a 2 in. x 3/4 in. PVC Schedule 40 reducer bushing which is connected to the 3/4 PVC Schedule 40 drainage pipe that flows back into the fish tank. The “bell” part of the siphon is cut from a piece of 4 in. x 10 ft. PVC Sch. 40 plain end pipe and a 4 in. PVC sewer and drain cap. More on bell siphons in a future post.
At the heart of the aquaponic system is a pump that lifts water from fish tank to grow bed. We chose a 400 GPH submersible pump from Amazon. All of the plumbing to connect the pump to the grow bed and used as irrigation was constructed using schedule 40 PVC 3/4 pipe.
Testing Out the Small-Scale Aquaponics System
So how does all this work? As water is pumped into the grow bed, it raises the water level to the point where it begins to trickle down the drain pipe within the bell siphon. As the trickle builds down the pipe, a vacuum is formed within the bell siphon which triggers a full powerful drain which empties the grow bed faster than the pump can fill it with water.
The siphon vacuum is broken when there is no water left to drain, air enters through the bottom of the siphon and the grow bed begins to fill again. This allows the grow bed to drain at regular intervals which is the purpose of a flood and drain system.
Lighting and Containers
Since this would be on a covered patio, we needed to install lighting over the grow bed. We used 12W LED replacements for T8 fluorescents from Home Depot since we wanted to reuse the T8 housing we already had. We also purchased 16 square plastic (5.5×5.5x6in) hydroponic pots for the grow bed from Hydrofarm. More updates soon!
Growing vegetables on a patio in dirt-filled pots seems like an easy endeavor, but theory does not always translate to practice. Why use aquaponics as an alternative? Let us explain.
Aquaponics vs Pots for Growing Vegetables
Following are challenges with growing in dirt pots: 1. you needed to carry dirt which is heavy — especially tough when you’re on the fourth floor; 2. the soil is devoid of nutrient content or it was mystery to the amount of nutrient content it contained; and 3. you don’t necessarily get enough sunlight for the plants to grow healthy since patios are usually covered. Sunlight, if you are lucky, comes in at angles, either in the morning or late afternoon. We discovered why so many patio gardeners try and fail — and probably never try it again.
Aquaponics using LED Lighting is the Solution
However, we didn’t give up and turned to what worked for us before, aquaponics using artificial lighting. Yes, water is heavy too but it can be poured with a hose and drained! And in regards to the nutrients, aquaponics is a mutually beneficial system where fish waste supplies nutrients (nitrogen) for plants, which in turn would remove these elements that would be toxic to the fish. More on the benefits of aquaponics here.
LED lighting is the ideal solution for dimly lit patios (or deck surrounded by lots of trees). Although expensive to purchase, they are low power consumers, could potential provide the right, if not perfect wavelength of light and be turned on and off using a timer so you have complete control of the growth using this lighting.
Growing Vegetables Using Two Organic Practices
During the last six years in Virginia, we grew our vegetables in 8 raised beds, filled with rich compost sourced from foliage, yard waste and surplus vegetables; and in two custom-built aquaponic systems. Read about benefits of using aquaponics here.
Our primary aquaponic system was a large installation outside which grew mostly stem plants such as peppers, tomatoes and basil using bluegill as the livestock living in a 600 gallon pond. We also had an indoor system which we grew mostly leafy vegetables such as bok choy, lettuce and arugula using tilapia as livestock in a 70 gallon tank.
Have A Fish Tank? You Have a Potential Aquaponics System
For our small patio, we needed to scale an aquaponics system even smaller. We decided to build an aquaponic system around an old 55-gallon tank we used as a saltwater aquarium. Like our larger systems in Virginia, we will build a flood and drain system, just on a smaller scale.
As we do our build, we’ll provide updates on progress on this page.
We’ve completed the basic structure of our Patio Aquaponics System. Our next step is to prepare and complete the aquaponic grow bed setup to properly test the water pump, plumbing, irrigation system and bell siphon to ensure a reliable flood and drain action.
Lining, Bell Siphon and Containers
As you may have read in our post detailing construction of the system, we’ve already lined the grow bed with 6 mil thick vizqueen — we also installed a custom-made bell siphon. For containers, we purchased Hydrofarm’s half gallon Vega Square Pots which measure 5.5×5.5x6in. This size allowed us to put 16 pots snugly in our grow bed.
Why Square Hydropnic Pots?
We went for a square-shaped pot to maximize the amount of hydroton we could load into the grow bed which provides more surface area for beneficial bacteria to reside to process the fish waste into nitrates and nitrite (plant food). So to fill about 8 gallons of net pot, we needed to purchase a 50 L bag of hydroton which provided more than needed.
Aquaponic Grow Bed Irrigation
After placing our hydroton filled pots, we installed the irrigation system made using 3/4 schedule 40 PVC piping in which we drilled 1/8 sized holes so water would be deposited into each of the pots. We wanted to spread water distribution equally to all the 16 pots in an attempt to equally spread solid waste since water was directly being pumped from the fish tank. The intent is for the hydroton-filled pots to also serve as solids filters, especially since we are going add red wiggler worms to the setup later to process the solids trapped in the hydroton.
Aquaponic Grow Bed Plumbing Test
We filled our 55-gallon fish tank with water and started up the 400 GPH hydroponic pump we purchased at Amazon. As expected, there were several leaks at the joints where we installed either elbows or t-joints so we sealed using plumbing tape. We chose to use tape vs PVC teflon sealant since we may want to disassemble the plumbing as we improve the system. Great news, it all worked! The 400 GPH provides a heavy flow so it took about two-three minutes for the grow bed to fill. The bell-siphon then took about a minute and half to drain the grow bed empty. Our next step is to purchase and introduce fish to the system to begin cycling the water.