How can I easily drain and replace the reservoir water?
(Culled all but the two strongest plants; I prefer to have only one per container.)
What is DWC?
Always start with half of the recommended dosage on the schedule provided with your nutrient system. For example, I use General Hydroponics Flora Trio, so I just use the schedule on the back of the bottle divided by 2.
Here’s the rule I use: If your grow room temperature is in a good range, then your reservoir temperature is also in a good range. You only really need to worry about your reservoir temperature if your grow room temperature is out of the acceptable range.
How many plants should I grow in a reservoir?
Although I haven’t confirmed this with every hydroponic nutrient company, colloquially, it seems that there is no problem at all with storing pH’d nutrient-water for up to a week as long as the nutrients don’t contain organic ingredients (like guano, kelp, bloodmeal, bonemeal, etc).
As a general rule of thumb, you should completely change your reservoir at least once every two weeks in the vegetative stage, and at least once a week in the flowering stage.
How should I start seeds in DWC?
Above the root-zone the plant grows normally, though with enhanced speed and yield thanks to the optimised conditions in the root area. The nutrient bath will need replacing frequently, especially as the plants mature. As with other grow methods, the nutrients tend to slowly increase in strength as the plant develops.
The main attractions of growing DWC cannabis are the fast growth rates and huge yields that are potentially on offer when DWC is done well. For those that delight in the joy of growing their own cannabis, there is an undeniable satisfaction that comes from seeing a successful DWC grow really push the cannabis plant right to it’s limits.
Deep Water Culture (DWC) is the technique of growing cannabis plants with their roots growing in a bubbling (aerated) nutrient bath. Growing cannabis in a DWC system is claimed by many to be the fastest way to grow heavy yielding cannabis plants. However, the technical complexity of correctly maintaining the pH and concentration of the nutrients does place certain requirements on the grower. DWC cannabis growing offers great rewards, but it is far from the easiest grow technique to master.
Many serious growers change the nutrient bath at fixed schedules, often weekly. You may be able to leave your nutrient bath 1-2 weeks between changes in veg. But in bloom, with hungry plants you should aim for complete weekly nutrient bath changes at a minimum. Pro growers may change baths even more frequently than that. They will check their baths once or twice a day in late bloom, topping up with nutrients.
The benefits of growing cannabis with DWC
But for someone that has only grown in soil before there are some undeniable added new complexities to consider. You will need a, perhaps slightly noisy, air pump to feed the DWC air stone and you may need to discover the joy of owning and calibrating pH and EC meters for the first time.
Growing in a DWC cannabis system isn’t for everyone. But for those that do it well, dry yields of several hundred grams per plant are quite routine. Deep water culture cannabis growing pushes hydroponics (soil-free) cultivation to it’s limits. As such, it’s the ultimate thrill and ultimate challenge for many indoor growers. For those that truly enjoy their cannabis cultivation there are few more satisfying feelings than seeing a crop grow from seed to harvest. When you harvest your first DWC monster the joy and satisfaction will be remembered forever.
The container is often simply a deep bucket (hence the name, DWC) which is often black in colour. The absence of light keeps dreaded slime and algae to a minimum. One plant can comfortably fill the typical 15-20 litre DWC bucket full of cannabis roots by the end of the grow. A healthy root ball is a huge white mass of roots.
Growing cannabis in DWC system
A DWC cannabis grow comes in many different styles and adaptations. However the common theme is that the roots are immersed in a bath of nutrients at an optimum pH, often around pH 5.8. Normally cannabis roots left in water/nutrients would eventually rot. But the presence of bubbling air (e.g. from a DWC air stone, connected to an external air pump) provides the roots the oxygen they need to grow with great vigour.
The most obsessive DWC cannabis growers change the water daily towards the end of bloom, though this would be considered excessive by many. However one primary reason why growers like to keep a fresh bath is because the cannabis roots may not use up all the nutrients and NPK minerals in your DWC nutrient line up at exactly the same rate. That means your nutrient bath could suffer an unhealthy accumulation of certain minerals. This can slow down the uptake of other nutrients. The result is a plant that struggles to grow with the nutrition it needs.