Aquaculture is what it sounds like—agriculture in water. The practice of growing fish, water plants, and shellfish instead of gathering them from the wild has been growing in popularity for decades, both industrially and in home settings, and has expanded to include combinations of species from aquatic ecosystems and traditionally land-based farming.
The possibilities are myriad, from recreational design, to sustainable homesteading, to commercial farming, and the technology and community resources are improving steadily.
Like other kinds of farming, aquaculture can be deeply rewarding on any scale, but it has a learning curve, and it takes work to get right. Here are some of the basics to get you started on your aquatic journey, or help you figure out if this water world is right for you.
Aquaponics is a branch of agriculture that embraces hydroponics, combining aquatic creatures and plants to create a virtuous cycle. These systems pass nutrients in a circle of life—the fish feed off of the plants, and the plants get sustenance from the waste of the fish.
Some people create purely recreational aquaponic systems for the joy of water gardening, never eating the fish or plants they cultivate. Others grow edible creatures and plants and harvest the fruits of their labors for home consumption or sale.
Aquaponics can also feature both edible and functional elements—for example, a system that grows lettuce, kale, or spinach in water that flows through a goldfish tank for a constant stream of fertilizer.
Successful aquaponics takes a little more than just running fish water through a tube garden, however. While it's true that true fish poop is fertilizer, you can't just toss fish poop straight onto plants or roots and expect to get anything sustainable or non smelly.
Nitrifying bacteria are the crucial middlemen that break down much of the fish waste, most notably removing the harmful levels of ammonia or nitrite and converting them to usable nitrates, which is what plants crave.
Marine aquaculture is a division of aquaculture that uses salty ("brackish") water, which many aquatic species need to survive—notably some popular varieties of prawns and fish. On the industrial scale, mariculture can take the form of net enclosures in the open ocean. At home, sea-water creatures and plants can grow in salty ponds.
Where possible, some home marine aquaculture systems pipe in actual ocean water, which offers the benefits of boosting the food supply with tiny natural organisms, and reducing the expense of creating and maintaining the saline balance locally.
Mariculture in home ponds removes the challenge of dealing with predators at sea, and offers greater control over water quality, allowing for the introduction of filters to control nitrogen levels and remove or redirect animal waste.
Outdoor vs Indoor Aquaculture
Outdoor aquaculture systems are easier to maintain year round in places that stay relatively warm. Indoor systems can function anywhere on a variety of scales, but involve the added expense of maintaining safe temperatures for your stock.
A common way to split the difference is to build in greenhouse-like structures, capturing the heat and light of the sun for your plants and creatures, as well as for the micro-organisms in the water.
One of the tricks to successful aquaculture is getting the temperature of the water just right. The sweet spot will change based on the types of fish and plants you choose to breed, but you’ll likely need to find a way to keep the water around seventy or eighty degrees. If this doesn't happen naturally in the environment where you live, more plumbing and heating will be necessary.
Something all DIYers should consider is that sunlight, like other sources of UV rays, can gradually break down PVC piping if it's not coated or painted in a dark covering. Sunlight can also encourage excessive algae growth, which, depending on the species in the system, can be a detriment, so outdoor aquaculturists should take that into account.
Indoor aquaculture is often done on a smaller scale, and often doesn't involve eating the fish you grow. Indoor aquariums usually feature a tank and smaller, decorative fish—like goldfish, betas, or other pet store classics.
If you use an indoor aquaculture system to produce food, you’ll likely use it either primarily or exclusively to to grow plants. Your fish tank, in this case, becomes a nutrient factory for your garden, which can be planted in pipes or high drainage soil media like stones.
You'll need some special plumbing to pump the aquarium water through the growing mediums, since plants in these systems are typically not directly on top of the water.
Cage or Net Pen vs Pond
Your next question is whether to employ small, large, or mixed containment structures. Cages and net pens keep fish in small enclosures, sometimes within larger bodies of water, while free-range ponds allow them to roam in a bigger space.
The advantages of cages and net pens are greater localized control. The drawbacks are that water quality is even more challenging to maintain, since fish will be raised in much tighter quarters.
Feeding, cleaning, and water monitoring will all require closer observation in cage and net pens, but you'll also have more control of each individual growing area, allowing you to experiment with different approaches and stock.
If you want a replenishing system where you don't just stock and raise fish, but also breed them and have new babies, separate tanks, ponds, or enclosures are necessary to separate the little guys from the adults. Typically these are called "fry," and segments of a system used for them are called "fry feeding tanks/setups."
Another pro to maintaining separate enclosures for smaller batches of stock is that it allows you to quarantine sick fish, or acclimate new fish that get added to your system. New fish can bring in diseases or pests like microscopic snail eggs on their scales. Certain snail species reproduce so aggressively in aquaculture settings that they can get everywhere—gumming up filters, and requiring draining and starting from scratch.
As with many things, the best approach here probably involves a mixture of elements. A communal pond setup works well for allowing beneficial bacteria to develop extensively, and incorporating systems that can accommodate partitions for separate cages or tanks are ideal for maximum control.
The cornerstone of a successful aquatic farm is frequent, thorough testing. Determining and maintaining water quality and characteristics might be the most challenging aspect of aquaculture.
Especially in the early days while you're getting your systems established, you should conduct testing every day, so you'll need a robust sensor kit and the know-how to use it. This is the steepest part of the learning curve, but once you get into the habit, it won't be as tough as it sounds.
You'll need to know the pH levels of your water, the dissolved oxygen levels, the conductivity levels, and the amount of ammonia and nitrate ions, and you'll need to make necessary corrections promptly to avoid injuring the life forms in your system.
One point of chemical clarification—fish waste produces ammonia, (Nitrogen-Hydrogen-3) which is toxic to them, and distinct from ammonium (Nitrogen-Hydrogen-4) which is relatively safe. Some kits and sensors can detect "total ammonia," which includes both ammonia and ammonium, but in the context of aquaculture the ammonia is more important to track and limit. The ratio of those two substances are largely regulated by pH.
Total dissolved solids, or TDS, are also critical to measure, as they affect filter strength, pump longevity, and nutrient uptake in plant roots.
In many aquaculture setups, it's considered good practice to prime your system by running water through it for a few weeks with innoculants like kelp, sea plants, ammonia, or beneficial spirulina before adding fish.
Stocking fish too densely or too soon can mean your system won't have enough bacteria to break down sufficient nutrients for your plants. Overstocking early can also be bad for your fish, since the water and waste need time to go through the nitrogen cycle, or they'll end up recirculating toxins.
Take the time to create healthy, safe, conditions, and introduce fish gradually to make sure you keep things that way.
Aquaculture Related Skills
Once your fish farm is up and running, you might want to invest in some additional DIY skills like fish canning, which will help you save your harvest for a rainy day. Alternatively, if you discover you still want to catch your own meal, but that aquaculture isn’t for you, maybe it’s time to give fly fishing a try.
If you have an aquaculture system you're proud of, we'd love to see it! Please consider sharing it on our projects pages to inspire others who are just getting started. We wish all you water farmers continued good luck and happy harvesting.