Are you in the hydroponics game to grow enormous tomatoes and hyper-productive peppers? Then you need to check out Deep Water Culture (DWC for short).
DWC is a hydroponic growing method that combines a large container and nutrient-enriched water solution with an air stone and air pump. This creates an oxygen-rich environment for the plant roots to grow in, resulting in better nutrient adsorption and bigger, healthier, more productive plants.
We’re going to be taking a look at all the details in this post on DWC hydroponics for beginners.
Let’s get started!
What is Deep Water Culture?
If you’ve read our guide to Mason jar hydroponics, you learned about a variation on the Kratky method that’s great for growing leafy greens on a small scale.
The Kratky method is entirely passive, requiring almost no real effort on your part past the initial set-up. This also makes any Kratky set-up short-lived, since the plant consumes all the nutrients and water in one life cycle.
This is the main reason why fast-maturing crops like leafy greens are the best candidates for Kratky hydroponics.
On the other hand, DWC uses a powered component (an air pump), making it an active system that you can maintain and adjust over a longer timeframe. DWC also uses a larger water reservoir, such as a 5-gallon bucket or large plastic tote.
Thanks to the aeration and water movement, plant roots in DWC absorb nutrients more efficiently, leading to the need for less fertilizer overall.
So DWC is ideal for plants that produce fruit and have a longer growing season, like peppers or tomatoes.
DWC requires a little more involvement on your part to maintain a proper pH balance and water level.
Still, DWC is very popular amongst home hydroponics growers thanks to its relatively simple and cost-effective setup, and because of the fast-growing and large yields it produces.
Supplies to Start a Deep Water Culture System
Let’s take a look at the basic supplies you need to get your own DWC system set up:
1. Container (a.k.a. Reservoir)
You’ll need a fairly large container for this system because your plant roots will grow quite large.
Choose a dark-colored, opaque container to keep algae from growing in your DWC system.
2. Air Pump
This is the mechanism by which you will cycle air into the water, increasing its oxygen content and thus its availability to the plant roots.
This one from EcoPlus is a good option to consider. You can find air pumps at aquarium or pet supply stores.
Use a length of ⅛ inch air line tubing to connect the air pump with the air stone (see below).
Air line tubing is more flexible and durable than other types, and selecting an opaque tube over a transparent tube will prevent the growth of algae inside of it.
This one from SMC is a good choice.
4. Air Stone
This is the delivery method for the air into the water.
The air stone rests at the very bottom of the reservoir, allowing the air from the pump to bubble up through the whole volume of water.
Look for air stones at aquarium stores, or online. Here’s a DWC-friendly option to look at from Amazon.
5. Growing Media and Net Pot
All hydroponic systems use a soilless growing medium and a net pot. These function together to anchor the plants’ roots and hold them suspended over the reservoir.
Our favorite growing medium is hydroton, which are expanded clay pebbles. These are pH-neutral, widely available, and reusable. These organic clay pebbles are especially well-suited for growing veggies.
A net pot, with its highly perforated sides, allows a strong and expansive root system to grow. We like this brand.
So just what can you grow with DWC?
You have quite a few options. Candidates for DWC growing include:
- Bok Choy
This list is by no means exhaustive, so don’t limit yourself to these! Part of the fun of hydroponics is experimenting with what works and what doesn’t.
The picture below is a general idea on how the DWC setup would look like:
Best Fertilizer for Deep Water Culture
Hydroponic systems require specialized fertilizers that meet specific criteria:
- Contain high levels of necessary nutrients
- Totally free of algae or bacteria
Let’s look at each one in more detail:
Just like plants growing in soil, plants growing in a hydroponic system need fertilizer.
This fertilizer should contain the three essential macronutrients:
Your plants also need secondary macronutrients:
When these 6 elements are combined, they’ll make up the bulk of the fertilizer.
However, high-quality fertilizer should also include the essential micronutrients:
Your plants use these elements in much smaller, sometimes almost trace amounts. But even those small amounts are vital for plant health and production.
For the beginner, an easy plug-and-play DWC nutrients source like General Hydroponics’ Flora set is optimal.
This set is broken down into three bottles that contain, respectively, primary macronutrients, secondary macronutrients, and micronutrients. This allows you to provide the right amount of each for your different crops.
For an even deeper dive into hydroponic nutrients, check out this video from commercial hydroponic grower ZipGrow:
A proper hydroponic fertilizer will also have a balanced pH. Generally, it should have a value between 5-6, although you can further customize pH to suit individual crops.
Having a nutrient solution with the right pH will make sure that those nutrients are soluble in the water. That means that they’re fully dissolved in the solution and thus fully available to the roots.
Unlike other forms of agriculture, hydroponics is by necessity non-organic.
Organic substances used for fertilizer, such as manure, blood meal, bone meal, fish emulsion, or even green plant-based manures, contain far too many contaminants.
Even though these contaminants are naturally occurring and harmless in a soil-growing setting, in a hydroponic system they will inevitably introduce algae and bacteria.
A hydroponic system needs to be as sterile as possible.
NOTE: If a sterile, chemical-based growing system isn’t exactly what you had in mind, take a look at aquaponics. Aquaponics expands on the concept of growing in water with the extra element of a fish tank, creating a symbiotic ecosystem in which the fish feed on the plant roots, and the fish waste nourishes the plants.
We’ve covered this in much more detail on our post comparing hydroponics and aquaponics, so stop by to learn more!
Setting up a Deep Water Culture System
Now that you know the basic approach to DWC growing, let’s talk about how to set up an actual, physical system:
Setting Up Your DWC Reservoir
First, take your reservoir – 5-gallon bucket or plastic storage tote- and place it in a well-lit location with a fairly consistent temperature.
If that location is indoors, we recommend using grow lights on a timer to provide enough light on a “natural” circadian schedule.
We like this full-spectrum light from ViparSpectra.
Then, take the lid off your reservoir and cut out one or more holes, using the inner diameter of the lip of your net pots as a guide. The net pot should fit snugly in the hole, with the lip resting on the lid hole.
A power drill with an appropriately-sized hole saw attachment is the easiest way to get this done. This hole saw kit provides plenty of options for whatever size net cups you choose to use.
Take note of how big and how many plants you want to grow before you cut holes.
A 5-gallon bucket is large enough for:
- One tomato plant OR
- One squash plant OR
- Two to three chard or kale plants
A storage tote has a much larger capacity, and you could feasibly grow up to eight plants together in each one.
After drilling your holes and rinsing to remove any leftover plastic bits, place the air stone at the bottom of the reservoir. Connect the tubing to the air pump, and plug the pump into a power source.
To prevent electrical catastrophes, take a page from the fish-keeping world and plug all electrical components into a surge protector instead of just straight into the outlet. We like this water-resistant one, which is suitable for indoor or outdoor use.
Fill Your Reservoir
The water level of a deep water culture system should indeed be pretty deep!
Fill the reservoir so that the water covers the bottom inch of the net pots. This will provide nutrients and hydration to the seedlings as they’re starting out.
(As the plants get larger, adjust the DWC water level down. This is both so that the roots keep growing down after the nutrients and so roots can absorb oxygen from the air.)
Follow the dosage directions of your chosen nutrient fertilizer according to the type of plant and add it to the water.
Now you’re ready to place the hydroton clay pebbles in the net pots and situate your seedlings within those.
Then sit back and watch your plants grow!
Maintaining Your Deep Water Culture System
Plants grow best in water that is between 60 and 65 degrees Fahrenheit.
This temperature is warm enough to encourage root growth but low enough to keep pathogens from developing. A colder water temp will stunt growth, while a higher water temp will be less oxygenated.
Monitor pH Level
Routinely test your water to make sure your system is in the proper acid/base balance. Remember that the proper pH value means that the maximum amount of nutrients are available to your plants’ roots.
The pH testing and troubleshooting process is easy, fortunately. Take a water sample, test it and amend as needed.
This kit from General Hydroponics has everything you need to keep your DWC balanced and healthy.
Some growers opt to clean their tanks weekly, and some push it to three weeks. To strike a happy medium, plan to clean out and refresh the reservoir solution about every two weeks.
Of course, if you notice any off odors or see any algae growth, clean the tank immediately, regardless of when your regular cleaning schedule.
Rinse your reservoir in between adding new solution to remove any leftover nutrients that might cause an imbalance when combined with new nutrient inputs.
Harvesting from Your Deep Water Culture System
Harvesting from a hydroponic system is a lot like harvesting from a traditional garden.
Pick things like tomatoes, eggplants, and peppers when the fruit is well-colored and ripe.
For leafy greens like lettuce, chard, or kale, remove a few leaves at a time so that you’ll be able to keep harvesting from the same plant for a few weeks.
We do recommend using scissors or a knife to cut away what you want to harvest to reduce tugging on the root system.
Potential Problems with a Deep Water Culture System
Algae growing in DWC. Algae is a result of airborne spores replicating within the nutrient-rich solution of a hydroponic system.
Algae is a problem because it drastically reduces the amount of nutrients and oxygen available to your plants, slowing down their growth until eventually it stalls altogether.
If you find algae growing on the inside of your reservoir or the roots of your plant, harvest what you can. Empty the system and sanitize the reservoir, lid, net pots and grow medium.
Then, try again!
For prevention, use distilled or filtered water to fill your reservoir, and make sure to keep any light from reaching the solution.
Slow growth. A slow growth rate in your DWC system can be due to a few factors, including these:
- Water temperature
- Available light
- Nutrient availability
- pH level
So if your plants are lagging, do some troubleshooting to adjust for these factors.
Bring your grow lights down closer to the plants, raise the water temps, and replace the water and nutrients in the reservoir.
Remember that hydroponics is kind of like a science experiment!
Food safety. The warm environment of any hydroponic system can invite the growth of pathogens and bacteria.
So it’s critical to wash your hands before working with your system, sanitize any tools you use, and rinse harvested produce really well before consumption.
You can sanitize your DWC system between plantings by using a solution of chlorine bleach: 1 tablespoon of bleach in 1 gallon of water
After sanitizing, allow all parts of the system to air-dry before reassembly.
3 Variations on DWC
1. Bubbleponics vs. Deep Water Culture
The adorably named bubbleponics system is essentially a DWC setup, with a reservoir, air stone and air pump. But it also has the addition of a drip system into the net pots that feeds the nutrient solution directly to the roots.
This lasts for the first few weeks of a seedling’s life, giving it an extra boost at the start.
Then when the roots are long enough to reach the water, you can turn off the drip and let them pull nutrients directly from the solution.
2. Recirculating Deep Water Culture
A recirculating DWC is a system that allows you to scale up production without scaling up time and effort.
In this method, you can connect several buckets or tubs with a circulatory system of pipes, and then feed all these sub-reservoirs with nutrient solution from one primary reservoir.
This means that you only have to calibrate and change the solution in one reservoir instead of multiple ones.
3. Deep Water Culture Cloning
You can also use DWC to clone your favorite plants by employing some liquid rooting hormone, like this popular one.
This concentrated hormone triggers plant cells to begin producing roots. And in combination with the nutrient-rich solution of a DWC, cloning can result in your cuttings growing an extensive root system in a short amount of time.
Frequently Asked Questions about DWC for Beginners
DWC is a fantastic way to get started in home hydroponics and produce food year-round.
All it takes are a few simple supplies and a small time investment, and you’re ready to discover the growing secrets that work best for you!
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