Deep Water Culture (or DWC) is a type of hydroponic growing system, where the roots of the plants grow into a reservoir filled with oxygenated water, supplemented with nutrients. Due to its efficiency, cleanliness, and speed, DWC is one of the most popular ways of growing marijuana indoors.
Maintaining the aerated water at the perfect temperature is one of the most common headaches for the hydroponic grower. Essentially, your goal is to get as much yield as possible, while simultaneously keeping the danger of infection and disease at bay. Let’s see how you can make this process as easy as possible!
The Ideal Temperatures for Deep Water Culture
Most hydroponic growers prefer their reservoir water to be at lower temperatures, as cooler water usually is more sanitary and contains higher levels of dissolved oxygen. Therefore, you will find that most guides will recommend a spectrum between 15-20ºC (60-70ºF). While this is not wrong, it is true that cannabis can survive in slightly warmer temperatures, as long as the organisms that prevent root rot from forming, stay alive.
Realistically, you can grow cannabis just as efficiently by maintaining a steady temperature of around 22-25ºC. These temperatures will not harm your plants and will actually help them grow faster, provided that you use a supplement to aid the development of root rot-fighting microorganisms, such as Bacillus. Beneficial Bacteria is an excellent supplement for your DWC crop.
However, if you don’t want to spend the extra money on supplements, stick with cooler temperatures. In the next section, we will look at how we can do that.
Maintaining a Perfect Temperature
Cooler temperatures are harder to maintain when you have a big heating lamp running for 18 hours straight above your plants. Generally, when the temperature in your grow room is normal, your reservoir water should be ok. However, there is no way to monitor and control temperatures at all times, and there is every chance that something might go wrong. That’s why we’ll be looking at some ways in which you can simplify (and possibly automate) some of these processes.
Increased temperatures caused by the grow lights can, in turn, increase the temperatures around the roots. When that happens, the amount of dissolved oxygen decreases. And where there is no oxygen, harmful bacteria thrive! Luckily, there are quite a few things you can do in order to prevent this from happening, depending on your budget and time.
The Expensive (More Costly) Option: Chillers
These devices are pricey, but they are your best bet when it comes to cooling down your reservoir. They operate exactly like an A/C unit, but underwater: You just plug them, turn them on and watch them work! If you think you can do it, you can try and build one of your own by following the instructions here.
Some of the best models currently on the market are:
Most of these units can be programmed to work under certain circumstances, so you don’t have to keep an eye on them constantly. Just set them up and let them do their thing! For best results, you can combine them with an automation system such as the BlueLab Guardian by Current Culture. This gadget allows you to monitor all aspects of your grow room wherever you are, via mobile connectivity!
The Quick and Cheap Fixes: Paint The Reservoir White and Offer Shade
Darker colors absorb more light and tend to build higher temperatures. That’s why in the summer, you should avoid wearing all-black. In a similar fashion, using a white spray paint all over your reservoir can reflect quite a lot of light and decrease the temperature by a few degrees. Similarly, you can quite simply protect your container by adding a layer of reflective material on top. Aluminum foil on a cardboard can work wonders in keeping your reservoir sufficiently cool.
The Swamp Cooler
This is an easy one: A small fan blowing gently across the top of the reservoir can decrease the temperature significantly. The drawback is that you will need to top up your water more frequently, as this method will cause water to evaporate at higher rates.