By Luke Sumpter

Sebastian is more than just a talented cannabis grower and photographer; he’s an expert on the art of deep water culture (DWC) cultivation. We sat down with him to understand what it takes to get the most from DWC systems, including crucial watch-outs, top tips, and advice for beginners.

1. Based on your experience, what are the main advantages of growing with a DWC system? (1:45)

I think the good thing about deep water culture is that it doesn't matter if you're an experienced gardener or a beginner. If you follow a few steps, you can get into it pretty quickly. It's not complicated because, in the end, it's a very simple setup, and it behaves differently in different growth stages. 

2. You have experience with autoflowering strains as well. Can you tell us a little more about that? (4:21)

Autoflowers are on the rise because for regular home grows, these plants make a lot of sense. They're quick, and they're easy to get into. You don't need to follow a certain light schedule. You can just throw the seeds in and watch them grow. Nowadays, there are some really good genetics, and the flavour is really good too.

Sitting Down With DWC Specialist Sebastian

3. How often should we renew the water reservoir in our DWC system, and at which temperature should it be? (7:12)

Changing the reservoir also depends on the phase of growth you're in. You should change it maybe once a week; I would say every seven days.

As long as you give them support and you have something to keep away root pathogens or whatever, your plants should be fine at a moderate temperature. Of course, oxygen levels decrease when the temperature rises, so it's not good to have very high temperatures.

4. What are the optimal pH and ppm/EC levels for a deep water culture system? (12:13)

The pH level should be anywhere from 5.5 to 6.5, as a rule of thumb, and the EC level depends on what stage of growth plants are in.

5. How do you keep check on the oxygen level in the nutrient solution? (14:13)

I don't check it at all, to be honest. You certainly can check your oxygen levels, but I feel like if you have a good-sized air stone, the pump is running 24/7.

For me, it was never a problem. If you use a decent-sized stone, the oxygen level should be more than enough in the water. I never had the need to measure or monitor it.

Sitting Down With DWC Specialist Sebastian

6. The air pump is likely to be the noisiest part of the setup. What can we do to make it quieter? (16:26)

What you can do is build a silencer box. It’ll serve the same purpose it would with an extractor. It's the same principle; you just build a wooden box big enough for the pumps. If you run multiple big pumps and build a bigger box, use some acoustic foam for the inside, and build a box that just closes up to the leads. And then just make sure there's enough air circulation for the pumps to draw air in.

7. What is the most important thing we should have in mind for each phase of the cannabis life cycle (germination, growth period, flowering period...)? (18:15)

I think feeding is the most important because it involves the critical part of your plants getting enough of the right nutrients. And, of course, the pH has to be in the right range; as we said before, 5.5 to 6.5 is ideal. The amount of light that you give your plants is also important. At the beginning, when they're very young seedlings (I start them in Mason jars), they don't need much light. You can run them under very small lights to get them started to grow pretty rapidly in deep water culture.

"The good thing about deep water culture is that it doesn't matter if you're an experienced gardener or a beginner. If you follow a few steps, you can get into it pretty quickly."

8. The main concerns seem to be centreed around unwanted organisms (as we’re not using any medium, bugs and other cannabis pests could latch on), pumps getting clogged, pH imbalances, transplant shock (when there’s no return point), and root rot. How can we solve these issues? (34:24)

Your container has to be leak-proof and light-proof; there cannot be any light coming into the container. That's a big, big thing. Also, when you change your reservoir, really give it a good clean. Don’t just dump the old water out and put in a new solution. This will help to prevent unwanted organisms and pests.

If the pH is right and you use the proper hydroponic nutrients, you should have no problem. It can be an issue, however, if you try to run organic nutrients that are normally for soil.

9. What does a typical day growing with a DWC system look like? (45:51)

I check the plants first thing in the morning, because where I live now, everything is solar-powered. So I'm off-grid. The first thing I check is pH and EC. I would recommend writing it down for each plant. Then, in the evening, you check it again and write that down too.

I enjoy as much time as I can outdoors in the mountains. Hiking, driving around in the mountains, going down to new tracks. It’s a beautiful life.

Sitting Down With DWC Specialist Sebastian

10. How important are the strains you use? (53:50)

That depends on what you're going for. For deep water culture, you may have to make some decisions based on the nature of the environment. As you will see much more rapid growth, you need to adjust to that and see what the strain does. For example, if you try to grow a 100% landrace sativa in deep water culture, you will have massive space problems as a home grower. Because even in soil grows, they can become extremely big extremely quickly.

I had a Purple Queen Autoflower from Royal Queen Seeds, which was, till now, still the biggest autoflower I’ve grown. I had a massive, massive producer that also had some Critical genetics in there, and that one grew amazing in hydroponics and deep water culture.

11. What’s your advice for newbies growing with this system? (57:30)

Before you start something like this, try to educate yourself. If you like a certain type of growing style or plant, maybe follow people on social media and just see what they do. It's not about imitating someone; it's about learning from someone who has actual results. Because you read a lot on the classic forums and people talk a lot about what they do, but it’s different to actually see it happen.

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