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Getting Started with Deep Water Culture

If you are just getting into the world of hydroponics, terms like “deep water culture” might sound fancy or even intimidating, and you may start to get the feeling that traditional soil-based gardening is more or you. But once you get beyond the surface of things you will find that really hydroponic growing methods are generally not complex at all.

Among the various methods of hydroponic growing, the most popular and also the simplest one is referred to as Deep Water Culture, DWC for short. Accordingly, this method is a good place to start for beginners, and we will provide an overview of the method below.

What Is Deep Water Culture?

In a nutshell, rather than having your plants roots rest in damp soil, the DWC method suspends the plants roots into an oxygenated solution of water and nutrients.

Because there is no soil, and no room for air to get in, the water needs to be well-oxygenated using an air pump or an air stone.

As for the water, one nice advantage of hydroponics is that you will never have to worry about watering your plants anymore, since they will be constantly sitting in water. And again because of the lack of soil to give the plants other nutrients, these nutrients must be added to the water. So with these three ingredients your plants can get everything they need without any soil at all.

The main difference between DWC and other hydroponic systems is that with the former the majority of your roots are going to be underwater 24/7, as opposed to some other systems which rely more on open air for the oxygen and provide water to the roots only periodically. This is why oxygenating your water is so important in DWC, because otherwise your roots will not be exposed enough to get enough oxygen from the air.

The Benefits of DWC

The main benefits of DWC, and also the reasons why it is so popular, are that it requires relatively little maintenance once it has been set up, the growth will be very fast in comparison to soil-based growing (as much as twice as fast in some cases), and the systems are relatively simple to set up.

Downsides of DWC

The negative aspects of this system can all be avoided with the right maintenance, however the kinds of problems that typically arise include: wild fluctuations in pH, water level, and nutrient concentration in smaller systems; it can be easy to over or under-calibrate when working with a smaller system; power outages may lead to your roots drowning since the system relies on electricity for the oxygenation of the nutrient solution; maintaining a consistent water temperature can be difficult.

Building a Deep Water Culture System

It is quite easy to build a DWC system. You just have to connect a pump to your tubing, connect the tubing to an airstone, and then place the airstone in a bucket. Then you simply fill the bucket with water, add your nutrients and properly pH your water. Once your seeds germinate and their roots hit the water, you should see a very impressive and quick growth. With this method your roots can suck up everything they need right away rather than growing longer in order to find pockets of water within their soil. And if you keep your water properly oxygenated, your plants roots will be able to survive underwater throughout their entire life cycle.

Recirculating DWC or RDWC

If you are planning to have a significant number of plants growing at once, then the traditional method described above might prove to be cumbersome: no one wants to maintain ten different buckets, checking and maintaining the nutrient balance in each individual bucket. Immediately you will imagine by yourself the advantages of having a central reservoir for one nutrient solution that then gets distributed around the your multiple buckets, and if you have done this already yourself you have essentially invented the RDWC method, or the Recirculating Deep Water Culture method. This way you only need to deal with oxygenation, nutrients, and pH balance at one source which then gets carried around to your buckets and then back again into your central reservoir.

DWC FAQ

What nutrients should I use for my solution in a DWC system?

– There are a wide variety of different hydroponics nutrients available, and you may eventually develop a preference for some brands or combinations over others. However for those just starting out we recommend using something simple and generic like the General Hydroponics Flora Series.

Is it better to use singular or modular system?

– For beginners it is recommended to start with a single reservoir setup. Modular systems are for more advanced growers who have a more exact idea of what and how much they want to grow.

Should the reservoir be sterile?

– Unfortunately it is difficult to answer this question with a simple “yes” or “no”. Some people prefer a sterile reservoir to avoid algae or harmful bacteria. Others, however, prefer not to use a sterile reservoir so that their plants don’t miss out on beneficial bacteria.

What’s the recommended pH and PPM / EC be for DWC?

– DWC doesn’t call for any differences in this department, so the start range of pH 5.5-6.5 is the norm here as well. Over time you will develop a more exact sense of what your particular plants need in your particular growing condition, but for beginners aim for the 5.5-6.5.
For your PPM / EC, we recommend not following the instructions on your nutrients, as they tend to be much higher than what the plants actually require. To start off, try cutting the amount listed on the packaging in half and see how your plants respond to that. It is easy to adjust upwards if they don’t respond well, whereas it is more difficult for your plants to bounce back if you go too high.

What about water temperature?

– As mentioned above, this can be difficult to control with DWC systems, but aim for between 60 to 68 degrees Fahrenheit, or 16 to 20 degrees Celsius. Any warmer than that and your oxygen level will drop off even with your air stone, and any cooler and your plants might think that the season is changing and that it is time to flower (which you may not want them to do yet).

How often should I change my nutrient solution?

– In general you shouldn’t wait longer than three weeks to change your solution, but the best time will depend on a number of different factors like: what plants you are growing; the stage of their growth; the size of the reservoir you are using. In general it is better to do a complete change periodically rather than simply adding more water and nutrient solution as needed.

​How do I test the oxygen level of my nutrient solution?

– You could buy a dissolved oxygen meter, but it is not recommended for beginners because the good ones are very expensive, and the cheaper ones are generally not very reliable. For beginners you are better off simply keeping your solution at the right temperature and running your air pump.

How much of the plants’ roots should be underwater?

– We recommend keeping about 1-1.5″ of root above the water line. You don’t have to worry about this part drying out because of bubbles from the air stone popping.

Are there any problems to watch out for that are specifically related to DWC systems?

– The following issues in particular are common in DWC systems, so make sure you monitor your plants closely: Pythium or other root-related plants diseases; sudden fluctuations in pH or PPM / EC / TDS; the nutrient solution becoming too warm.

How much faster will my plants grow using a DWC system?

– Assuming that everything is set up and maintained correctly, you can safely assume that your plants will grow by at least 15% faster than they would in soil. However it is not unusual to see even faster growing speeds, and personally I have had lettuce grow nearly twice as fast as the time it would have taken in my outdoor garden.

Which plants grow the best in a deep water culture system?

– Basically any plant that doesn’t need to flower will grow very will in a DWC system. Lettuce and herbs in particular can grow super fast and super healthy, making them extremely ideal for DWC. This doesn’t mean that you can’t grow things like peppers, tomatoes, or even squash using a DWC system, it just means that they will require some extra effort and care.

Any other tips you would care to impart to a beginner DWC grower?

– One of the best tricks you can use to help maintain different plants is to vary the amount of moisture in the root zone, since both a drier and wetter root zone can produce a variety of different responses. Dryer root zones, for example, can trigger the production of essential oils in fragrant crops like mint and basil (something they do in order to conserve water). A wetter root zone, on the other hand, can shifts your plants’ focus to producing vegetation, especially with large fan leaves. This will in turn speed up transpiration as well as photosynthetic potential.