Can You Grow Onions in Aquaponics?

Onions are a staple diet for millions of people around the world and are grown in a myriad of environments to add flavor and texture to many a dish.

The idea of growing onions in an aquaponic system is not only possible but maybe a preferred method of farming to achieve a growing system that would reap a more organic harvest than traditional outdoor planting.

You can grow onions in aquaponic systems. Flood and drain or Nutrient film technique (NFT) systems tend to work best as the roots of onions need plenty of moisture.

Let’s have a look at how this system would work.

Onions and Aquaponics

Growing onions in a field is a labor-intensive farming method and requires pesticides, herbicides, and chemicals to eliminate pests and diseases. And they need a lot of watering.

There are several new revolutionary ways to grow crops over the last few years that have enabled city dwellers to grow onions, fruits, vegetables, and even grapes in an urban environment. These methods have breached centuries of traditional farming and have, in many cases, made it possible to grow staple food products in areas previously unviable and unachievable.

All these systems rely on regular maintenance techniques and nutritional systems to assist in the growing process, and any failure in the chain can lead to a lost or diminished harvest.

In aquaponics, the best of each of these techniques are utilized in a controlled environment to nurture the growth of onions, while the downsides of many of them are discarded.

No pesticides or chemicals are used, the time-consuming maintenance process is eliminated and even the harvesting process is simplified.

Aquaponics is about harnessing the power of nature itself to create a self-sustaining eco-system. It works by converting the natural waste of fish into nutrient-rich water that is transported through the system to be absorbed by the roots of the onions, and then the cleaned water is returned to the fish tank.

Once the system is installed there is very little ongoing work or maintenance required. This closed-loop aquaculture works harmoniously with the onions and the fish flourish mightily within this self-contained eco-system.

How to Grow Onions in Aquaponics

Creating a continuous cycle is the tenet of aquaponics.

This particular method requires an aquarium, a pump to move the water back and forth from the aquarium to the roots of the onions, a grow bed where your onions will be located, and a selection of fish for the tank itself.

The grow bed can either be placed on top of the aquarium or off to the side. The grow bed, or flood table as it is also called can simply be a plastic tray or a large container as long as the support structure is strong enough.

Once you have decided on the location and how big you want your aquaponic farm to be, select the size of the aquarium. By using an aquarium instead of a solid container, gives you the benefits of having and enjoying your pet fish while growing your new onion crops at the same time.

At this stage prepare the fish tank as normal by dechlorinating the water and then allowing sufficient time for the bacteria to build up over the following weeks.

This is the starting point to set up your very own fully integrated ecosystem. It works by having the natural waste from your fish being broken down into nitrates, and then a pump carrying these nitrates to feed the roots of the onions. Nitrogen is then released by the plants, cleaning the water which is then safe to be pumped back to the fish, and then the cycle is repeated.

This process is on a continuous loop and the only time water has to be added is if there is a marked level of evaporation or if it is transpired by the plants.

Three Ways to Grow Onions in Aquaponics

There are essentially three types of aquaponics that are used depending on growing experience, the space available, and the scale desired.

The Deep-Water Culture Set Up lets the onion roots drop into the water and take nutrients directly from the water. This method is suitable for a larger scale operation.

The Nutrient Film Set Up is where the roots are left to dangle in a PVC pipe drilled with holes. The water is drawn into the pipe to run over the roots, delivering much-needed nutrients before being fed back into the tank. This method is suitable where space is a consideration and is flexible enough to allow crops to be grown vertically, horizontally, up walls, or even hung from ceilings.

The Media Bed Set Up is the last method and is the most convenient for home growers with little experience, and who opt for a smaller-scale operation. Here the plants are seated in a bed of expanded clay pebbles or gravel, and a pump draws the water from the tank to flow over the roots.

Normally onions require space between the next clove to grow as about a dozen shoots sprout above ground. In aquaponics the bulbs can be set a mere inch apart, allowing more to be grown in a smaller area.

Caring for your Onions in Aquaponics

Growing onions with aquaponics will give you the option to decide how big you want to grow, whether your intention is to feed a small household or a community of onion lovers.

It all depends on the size of the area you have available, from a ledge in your bedroom to a large greenhouse in a nearby field, and, of course, what your goals are. Even the strain of harvesting can be mitigated with the grow bed set to a height totally at your discretion for comfort.

Less water is used due to the closed-loop ecosystem, with hardly any at all being wasted. With this consistent water availability, the bulbs have a tendency to start sprouting quickly as long as the temperature range of between 55°F to 75°F is maintained.

Aside from the importance of having the correct temperatures, having the ph level right is just as crucial, but it can be a little tricky. The onions, the fish and even the bacteria being formed in the water are three distinctly separate living organisms, and all have different ph requirements.

This ph level can be affected by the fish waste, and that can adversely impact the ability of the plants to absorb nutrients, which will reflect negatively on the lives of the fish. So, as you can see the balance of the eco-system as a whole has to be finely tuned regularly.

The optimal range of ph for aquaponics is around 7.0. To ensure a continued harmonious system, it is advisable to monitor this neutral ph balance on a daily basis to avert any wild fluctuations and to keep within this ph safe zone.

And the type of fish selected for this project can make the task of maintaining your onion farm easier also.

One of the ideal types of freshwater fish to use is, believe it or not, is the humble goldfish. They tend to excrete large amounts of waste so your onions won’t be short of nutrients in the conversion process.

But koi can be used, as well as tilapias, and really any hardy fish will do that require minimum maintenance. After all, the beauty of aquaponics is not just the onions you will be growing tenderly, but the aquarium full of colorful, interesting fish that you will be enjoying at the same time.

Harvesting Aquaponic Onions

Aquaponics is a symbiotic relationship between plants and fish and goes hand in hand with sustainability. This collaboration uses less water which is cost-effective and good for the environment and produces 100% organic produce.

Really there is no limit to where your onion crops can be grown with aquaponics and an added bonus is that the growing times are accelerated. This results in a quicker crop of onions being harvested more frequently and, due to this system being so self-contained and self-reliant, the whole interconnected process becomes a game-changer in the field of growing onions.

All in all, aquaponics combines all the new innovative growing methods together with the flexibility to be scaled to fit over a small aquarium filled with an array of multi-colored fish, or scaled upwards for a much larger industrialized farming operation.

Can there be a better way to grow your onions?

Can You Grow Broccoli in Aquaponics?

When you first run either a hydroponics system or an aquaponics system, it’s hard to know which crops are best to grow.

The smaller systems lean toward shallow rooting vegetables, which are mainly herbs or leafy green sorts of vegetables for salads. However, larger systems can cater to larger crops, and with space, they are perfect for tomatoes, cucumbers, peppers, or other vining vegetables that need room to spread.

The question comes down to root vegetables and the possibility of growing them. You can find out the answer, and then other information about growing this healthy vegetable.

Can you grow Broccoli in Aquaponics? You can grow broccoli in your flood and drain media bed or Dutch bucket type system. You find broccoli isn’t so much a large crop; it is heavy. This weight makes it unsuitable for floating rafts, nutrient film, or other similar systems. It is worth growing in larger, supportive beds. However, there are a few other growing demands of this healthy crop you need to know.

Broccoli and Nutrient Requirements

To grow broccoli efficiently, they require lots of nutrients, and thus you may need to adjust the fish population to accommodate this crop.

You will also find it far better to attempt growing broccoli in aquaponic systems, which are well established. Fish levels may be better if they are around 1lb of fish per eight gallons of water rather than 1lb of fish for every 10 gallons.

With a perfectly functioning system, the nitrates’ levels should be 50ppm or as close to this as possible. Besides this, the levels of ammonia need to be low, even with increased fish density.

Besides this, the other two key nutrients are magnesium and phosphorus, or you may see crop growth slow.

Growing Instructions

When you come to transplant seedlings into your media bed, you ought to do this once they have 4-5 true leaves showing. Your crops at this stage will be around 5.5 to 8 inches tall.

The germination time to reach this stage can be around 4 to 6 days. Besides this, you need to consider the spacing for transplanting as broccoli comes with a large root system.

Seedlings should be planted from 17 to 20 inches apart from each other. Closer than this, and you can see your crops producing smaller central heads.

Growing Conditions for Aquaponic Broccoli

Broccoli is a winter vegetable and won’t take too kindly to growing conditions that are too warm. While it is a beneficial crop to grow, it is on the side of moderately difficult.

You can find seeds that will be bolt resistant to help, though trying to maintain the ideal temperatures will help considerably. Broccoli thrives the best in daytime temperatures of 57 – 62 F (14-17 °C).

Winter varieties will require temperatures around 50 – 59 F (10-15 °C) for the head formation. Temperatures above these are possible, so long as there is a higher humidity level available. Should temperatures be too high (over 65°F), this will cause premature bolting.

Also, broccoli likes full sun for around 6 hours per day. It can cope with a little partial shade, although this could make broccoli mature at a slower rate.

Broccoli can deal with swings in pH levels, although for the health of the rest of your system, aim to keep it at a more neutral level of pH 6 to 7. A digital pH pen is ideal for checking the levels frequently.

Harvesting Broccoli

It would be best if you started harvesting broccoli for the best quality when head’s buds are firm and taut. Harvest immediately when the buds separate and show their small yellow flowers. To preserve taste, it is important to harvest the broccoli in the morning.

You should cut the heads off your plants and take at least 6 inches of stems diagonally below the head.

Most varieties of broccoli have side shoots that develop after the chief heads are harvested. You can harvest from one plant for several weeks, sometimes, from winter to the beginning of summer as long as summer temperatures are not too hot.

Pests and Disease in Broccoli

Many crops in your aquaponics and hydroponics systems often face less intrusion of pests and disease. Although broccoli is one that, like cabbage, can be prone to the effects of cabbage worms and other pests.

Here are some pests or disease you will need to be wary of when growing broccoli in aquaponics.

  • Aphids: Curled leaves may show the sap from your broccoli is sucked up by insects. A way to combat this is to apply soapy water on all sides of your leaves whenever you see aphids.
  • Cabbage Loopers: If you see small holes in your leaves between the veins, they may result from green caterpillars. Check the underside of the leaves. You can pick these off by hand if the problem is small or fight the problem with Bacillus thuringiensis, a natural bacterial pesticide.
  • Cabbage Worms: Such worms, Whiteflies, or cabbage root maggots can be treated the same way as you treat any cabbage loopers.
  • Clubroot: Rapid wilting of plants can be attributed to this fungus. Your entire plant, including all its roots and tendrils, needs to be carefully unearthed and removed from your media bed. If roots appear gnarled and misshapen, then the root of the club is causing the problem. You will need to remove infected plants swiftly, so the fungus will not continue to spread throughout your system.
  • Downy Mildew: When purchasing broccoli seeds, make sure you purchase varieties resistant to downy mildew. Otherwise, you will spot the yellow patches that are caused by moist conditions. Aim to keep crops dry, and they have plenty of air circulation.
  • Nitrogen Deficiency: Broccoli is a nutrient-loving vegetable. If your fish tank isn’t large enough to cope with numerous broccoli plants, it could lead to a slight yellowing of the bottom leaves rising upward on your plants.

If you have the capacity, you can plant marigolds or calendula flowers close to your broccoli as these help fend off the above pests that take a liking to your crops.

Aquaponic Broccoli Varieties

While there are many varieties of broccoli available, not all are suited to aquaponic cultivation. Here, we have the top three to consider should you decide on broccoli for your soilless system.

Chinese Broccoli

Despite being a broccoli variety, it differs greatly from other cultivars because it grows without florets. Also known as Kai-Lan or Chinese kale, this variety has large, thick leaves with a bitter taste compared to Calabrese and sprouting broccoli.

Chinese broccoli grows quickly, at around 35 days, and thrives well in warmer environments, making it ideal for growing in the summer.

Sprouting Broccoli

In contrast to Calabrese, this kind of broccoli shows more stems and smaller single florets than a central head. Sprouting broccoli is more bitter than other species and can be purple or white.

White-sprouting broccoli is milder and slightly sweeter in flavor than its purplish equivalent.

Calabrese Broccoli

You will be more familiar with the Calabrese Broccoli since it is the most commonly sold variety in stores and markets. The heirloom plant was named after Calabria or “the toe” from the Italian peninsula.

Gardeners highly recommend it because Calabrese broccoli offers an extended harvest period, as it forms side shoots that remain in place after removal of the main head.

Conclusion

Although broccoli can be more challenging to grow than many other crops, so long as you have deep grow beds to offer support and maintain the desired temperatures, there is no reason you can’t dedicate a grow bed to this crop.

While it is usually a large grow bed, you can use a Dutch bucket system to make sure they have ample support. You then have the flexibility of your spacing and won’t waste valuable space in your main bed.

While a challenging crop, broccoli is worth the effort because of its rising costs in the stores and its many health benefits.

What Size Gravel is Best for Aquaponics?

In the same way that hydroponics is a soilless means of growing, so is aquaponics. One of the key differences being the way the grow beds are constructed. While hydroponics systems tend to grow in pots in various systems, an aquaponic system most often uses flood and drain grow beds, which are full of growing media. Gravel being the most common.

What size gravel is best for aquaponics? There are many sizes available, and in theory, any size gravel can be used. Most hydroponic gardeners prefer pea gravel, which is between 1/8 of an inch up to 3/8 of an inch in size. Although, the smaller 1/8 sized pea gravel being the gravel size of choice. 

Considerations of Aquaponic Growing Media

When you first build any aquaponics system, there needs to be a few considerations when choosing the ideal growing media. Here you can find the things you need to think about, and you can see why pea gravel is the ideal media to use.

Inert: Any aquaponic grow media needs to be pH neutral. Similarly, as a hydroponic system, the pH level in an aquaponic system needs to be controlled.

Fish and plants have their preferred range of pH range, and ideally, you need to aim for a range of pH 7. Many media can change the pH level, although pea gravel isn’t one of them.

All you need to do is thoroughly cycle your system before adding fish or plants to clean away any dust.

Grow Bed Depth: Any grow bed in aquaponics should be a minimum of 12-inches deep for most crops.

Weight: Any grow media in use in a hydroponic system should be too heavy to handle. It should be light to medium weight, so you can easily dig your holes when you plant your seedlings. On the flip side, if they are too light, they can float in the grow bed and won’t offer support.

Easy to Work With: Grow media can comprise any size or shape, although sharp edges are best avoided. If you use sharp-edged stones, these can be hard on the hands and damage any grow beds that are not constructed from solid materials.

Non-Decomposing: No aquaponic grow media should break down because it can work its way through your system and clog your water pump and reduce dissolved oxygen in the water for your fish.

Pea Gravel for Aquaponics

Pea gravel fits all the criteria and then some. The smaller pea gravel has a large surface area that bacteria can thrive on. With this, the nitrogen cycle is complete and, in turn, delivers robust plant growth.

From the fish waste, the broken-down compounds create ammonia, which passes around your system. Once it flows through your smaller sized pea gravel, it is converted into nitrites by two bacteria strains (Nitrosomonas bacteria).

From here, these nitrites are consumed by the second strain of bacteria (Nitrobacter bacteria) and converted to nitrates. Your crops then use the nitrates as fertilizer.

As there is more surface area on the gravel, a larger number of nitrates are being produced than if larger gravel was being used.

Pea Gravel with Limestone

Generally, your pea gravel won’t contain anything to change your aquaponic system’s pH level radically. However, if there are any traces of limestone, the results could be different.

Before filling your grow beds, you can carry out a test to check whether your bags of small pea gravel.

Take a handful of gravel, place it in a container, and then cover it with some white vinegar. You can see the vinegar fizzles if there are traces of limestone.

You need to avoid limestone as this will keep your pH above 8, which can harm your plants and your fish.

You can place some gravel in distilled water and check the pH after a couple of days, although it is better not to purchase any gravel you think may be suspect.

One thing to note is that the name pea gravel isn’t a type of gravel, it is because of its size. One dealer can sell something different to another.

Grow Bed Depth and Pea Gravel

One thing any gardener needs to understand when using pea gravel is the depth of the grow bed. The recommended depth is 12 inches, and for a good reason. When building a system, you may be tempted to go for a shallower bed.

Even while pea gravel is the cheapest media you can purchase, the amount you need could be considerable. However, there are reasons why you should opt for a grow bed of this depth, if possible.

Here you can see why avoiding the shallower bed sizes can be beneficial, and it is advisable to scale your system to support the larger bed and the increase in the size of the fish tank you will require.

You will face limitations if you decide to go for a shallow grow bed filled with pea gravel.

Eco-System & Dead Zones

In deep aquaponics grow beds, you naturally create a layered eco-system. One significant benefit of this is that you will prevent any ‘dead zones’ dotted around your grow beds.

Besides this, as you have a thriving environment packed full of beneficial bacteria, worms, and lots of space for roots to grow. You don’t have to clean out your grow bed.

These bacteria and worm communities, along with your plants, do all the cleaning for you. Anything less than 12 inches, and you won’t be able to reap these benefits of a stable eco-system.

Plant Limitations

If you are growing nothing but crops similar to lettuce, you may get away with a grow bed shallower than 12-inches.

However, if you grow indeterminate tomatoes, cucumbers, and corn among the many other crops that can benefit from aquaponics, these shallow beds can’t support them. You won’t receive the same base nutrients and beneficial bacteria for these longer living crops.

One thing not to forget is your aquaponic system can be highly configurable, and you can mix grow beds and use raft systems for short rooting crops and larger grow beds or Dutch becket systems for deep-rooted crops.

Three Zones of Pea Gravel Grow Bed

Zone 1 – Surface Zone

The top 2-inches serve two purposes. It allows for light penetration and acts as the dry zone to limit evaporation. The second reason for this dry zone in your pea gravel is to prevent collar rot and stop any algae forming as the nutrient-rich solution faces light exposure. Also, the infection from powdery mildew is minimized.

Zone 2 – Root Zone

It is in the second or middle layer where the plant activity occurs. Making up this layer is around 6 to 8 inches in depth. As you drain after flooding your grow bed, water drains away completely and presents highly efficient oxygen delivery to the roots, microbes in the soil, worms, and beneficial bacteria.

When you are in the flood cycle, incoming water will distribute all the fish waste particles containing nutrients through the entire grow zone. Worms are highly active in this middle zone, where they break down solid matter to release minerals and add to the underlying worm tea. On each successive flood and drain, this beneficial tea is spread around all your crops.

Zone 3 – Solids & Mineralization

Once you reach the bottom 2-inches, you find all the fish waste solids and worm castings are gathered together. By the time it reaches here, it will have been reduced by around 60%.

In each of your flood and drain cycles, this zone is kept fresh from the effective delivery of oxygen-rich water.

Conclusion

Once you see the benefits of using 1/8-inch pea gravel, you can understand why it is among the most popular media.

It is highly affordable, and any gardener is advised to lean toward the deeper grow beds when possible. Besides this, there is nothing you need to do with pea gravel, and it is one of the easiest materials you can work with.

There is nothing but benefits you can get from using this smaller sized pea gravel than if you used a larger gravel, or an alternative growing media.