The vast majority of people have heard of a cultivation method that is based only on a nutrient solution, without soil. In technical terms, this is Hydroponics, where the plants are grown directly in water without soil. Hydroponics is big business. Much of the romaine, crisp and heart salad you buy is often grown hydroponically. But more and more large nurseries and vegetable producers see the advantage of growing hydroponically. You get bigger crops, stronger plants, more energy efficiently and not least, up to 70% faster growth! But we will not deal with large water baths with hundreds of thousands of liters of water. Deep Water Culture is a highly valued method for hobby growers. It is easy to use, relatively cheap to get started with and very effective.
Deep Water Culture, or DWC as we call it, is a simple method to grow in. In principle, all you need is a bucket, air pump with air stones and a lid. But for good results, it is necessary to have nutrition adapted to hydroponics, plenty of air, large enough containers for the nutrient solution, plenty of light, fans for air circulation and a good climate. That will get you far. DWC is based on a carefully adapted nutrient solution to which oxygen is added from an air stone at the bottom of the container. The air will form lots of bubbles that add oxygen to the water while keeping the water moving. The container only needs to meet one criterion and that is that it is light-proof. This is to prevent algae and bacterial growth from light penetrating the solution. The food you use is concentrated and very strong. We usually measure in ml per 10 l of water. There are many different industries you can use. What they all have in common is that they are made to dissolve quickly in water, remain stable, do not react with bacteria and algae, and contain the right amount of micro-bacteria adapted to water cultures. Without air, the roots will rot in the water and drown. The secret of DWC is an insatiable amount of air that the roots get which leads to a large uptake of nutrients. Hence the effect.
There are several different methods to use. Bubbleponics, DWC, Undercurrent DWC etc., but here we deal with DWC in single containers. The advantage of a closed system is; easier to adapt the nutrition to each plant - in case of disease, bacteria or other infections in the water, it is isolated to just one plant - independent follow-up on each plant. The disadvantage is that it takes longer when changing the nutrient solution. Okay, let's get started.
- The easiest is to use an industrial bucket of 25 liters or more with a lid. Some stores that specialize in hydroponics sell these. Otherwise, they can be obtained from companies dealing with waste management or industrial plastics. It is important that they are made of thick plastic and colored so that no light is allowed to penetrate.
- Net basket (netpot). Pot with "mesh" in the lid. The roots of the plant will grow out of the net and into the nutrient solution
- You get air pumps in all sizes, and if you are running a system of 3-4 plants or more, a compressor is recommended. Cheaper and more efficient than the big air pumps. Try to find a pump that gives more than 4 liters of air per minute per outlet. Available in aquarium shops, hydroponics shops etc.
- There are many air stones to choose from. I have successfully used 6” disc stones. These give the best bubbles and movement in the water, but you can try it out. The most important thing is that it is large so that the surface the air comes out on is as large as possible, but at the same time not so large that the air from the pump is not sufficient to cover all the pores in the stone.
- Hoses that run from the pump, into the buckets and down to the stone.
- One of the most important elements. Plants need light, and the more light they get, the better they grow. 250-600w HPS or MH is preferable, but if one tries with a plant, some powerful T5, CFL or LED will do.
- pH meter. Digital pH meters can be bought at Clas, ebay, hydroponics shops, aquarium shops. You don't need to put so much money into them. But it is important to order enough calibration bag or powder.
- PPM or EC meter. I prefer PPM to EC and will deal with it further in this article. But what you choose is up to you. With these we measure particles per million parts in the water. This is necessary to know exactly how much nutrition you have in the water.
- pH buffer. We use this to adjust the pH value in the nutrient solution.
- Nutrition. There is a lot to choose from here, but I will deal with a couple further on in the text. This is a specially made nutrient that is adapted to hydroponic cultivation.
- Calcium, Magnesium and H2O2.
- Lecakuler or hydrothorn (volcanic rock)
The system put together is quite simple. In the lid, cut a hole that is the same size as the inner diameter of the net screw. On this curve you have a lip that lies and rests on the lid. One tip is to glue this firmly with Tec7 or silicone. Then you get more stability when the plant grows. On the side of the bucket, just below the lid, make a hole that is just big enough for the air hose that will go into the bucket. At the end, connect the air stone, which should lie flat on the bottom in the center of the bucket. The hose continues to the air pump. Keep the pump away from light and heat so that you do not pump hot air into the nutrient solution.
Step by step, chili
Take a piece of rockwool or a rockwool cube which you place in the center of the net basket. It is important that it is at the bottom of the net basket because it will absorb water from the bucket. Fill up with cleaned leca balls all around so that it is tight and stable. It is important that no light enters from any of the openings in the mesh. Put the seed in the rockwool. When we fill up for the first time, we only use water. Fill up so that the water goes barely a centimeter up the bottom of the net basket. Have something to stir the water with so that you can mix out the pH buffer in the water. Use the pH meter to check the value of the water. Typically it is 6 – 7.5 pH here in the Nordics. We want the water to last 5.8. Add only a few drops and stir well before measuring again. The amount of solution you need to add varies on the pH you have in the water from the tap and the number of liters the buckets hold. But one good tip is to take it slowly because it goes down or up quickly. When you have 5.8 in pH you are ready. Put the lid on and turn on the pump. The water will penetrate the rockwool and make it damp. The bubbles will supply enough water for a long time to come, even if the water level drops a couple of cm.
When the seed has germinated, you must switch on the light if you have not already done so. So far we only use water. When the 2 – 3 sets of true leaves appear the roots should start to stick out of the mesh basket. Then it is time to change the water and add some nutrients. Every time the water is changed, the buckets, hose and air stone must also be thoroughly cleaned. Please scrub with a scrubbing sponge. When this is done, we fill it up again with water until it hits the bottom of the net basket. But before you measure the pH this time, you must measure the PPM in the water. This varies greatly, but the rule is; the cleaner the water you have in the tap, the lower the PPM value. In my tap it is 67 PPM on average. We want a low nutrient level for these small plants. 80-100PPM is sufficient. Read on your preferred nutrition what they recommend in terms of quantity and draw this up with a syringe (5-10ml pump from the pharmacy). Let's say your water holds 50PPM straight from the tap. You will then have 130 – 150PPM in the water after the nutrients have been added. Put in some of the string you have drawn up, stir well and measure until you reach the value you want. When this is done, we measure the pH and adjust it to 5.8. Then just put the plant back in the bucket after the air is connected and the stone in place. As a rule, the water must be changed every 14 days. If necessary, you can top up with pH-adjusted water if it evaporates a lot within the 14 days.
As the plant grows at a terrific pace, we must increase the amount of nutrition. When the plant is around 10-15cm, we increase the amount of nutrients to 250PPM. Repeat the process previously described, but now you must also add 0.5ml H202 per liter of water and this is added after the pH has been adjusted. When the plant grows to around 30cm, we increase the PPM amount to 350PPM. Now we will also add magnesium and calcium. The amount depends on how strong a solution you have purchased. But as a rule, it is 1ml per liter of water. But only use half the strength stated on the bottle. So, it says 1ml per liter of water, you use 0.5ml per liter of water. Increase the amount of H2O2 to 1ml per liter of water and add this after the pH has been adjusted. For every 14 days you change the water in the future, you must increase the PPM amount of nutrients by 50PPM each time until you reach 500PPM. If your plant starts to grow up and set flowers, you can go to full strength on magnesium and calcium.
When the roots start to close at the bottom and form like a ball, the plant sets flowers, you can increase to 650PPM, full strength magnesium and calcium, 1ml H2O2 per litre. Now just enjoy the sight of the plant growing so fast you can almost see it. Along the way, it is good to trim the plant. Imagine that all leaves growing inwards towards the trunk should be gone. You want the plant to spread out at the same time as you want to give more light to the leaves if you remove the leaves in the middle. When you get to the stage where the plant sets fruit you can increase the PPM amount by 100PPM every 14 days until you reach 800 - 850PPM. At this stage you can stay on this strength for quite some time. But you will find that the plants drink A LOT of water, so you have to add pH-adjusted water up to several times a week. When you have a fully grown plant with lots of fruit you can increase to 1000PPM. Feel free to use nutrition that has been specially developed for flowering or ripening of the fruits. But again, this is entirely up to the industry you use. You will also find that the plant drinks extremely much. Just fill up and enjoy.
The road to success
Here are some tips, advice, rules and experience that I list.
- Make sure that the nutrient solution stays below 24 degrees. If it stays above 24 degrees, the pH buffer can become unstable, algae growth flourishes and bacteria form. This is critical to success!
- Always change the water at least every 14 days. Clean and wash the equipment before putting in a new solution.
- Make sure that it is between 22 and 28 degrees in the room where the plants are. Preferably have a drop of 3 - 5 degrees at night temperature.
- H2O2 is used to increase oxygen uptake, but perhaps more importantly it eats and dissolves dead organisms in the water and on the roots.
- Foods that are recommended are the GHE Flora series and BioBizz. This is a 3 part nutritional system that works very well. Flora Grow, Flora Micro and Flora Bloom. There is a good guide on how much of each nutrient you should use for the different stages. Use the distribution as directed, but stick to the PPM values and not the ml values stated on the bottles. Typically there is more of Flora Grow during growth and more of Flora Bloom during flowering/fruiting. I also tend to use Flora Ripen in addition when I have a lot of fruit on the plants. BioBizz has an organic 3-part series that is just as good, if not better.
- When the plant has produced hundreds of fruits and has been at a high PPM for longer periods, it may be good to pick off all the fruit, cut the plant down well and flush it. With flushing, you run the plant in only water, magnesium, calcium and H2O2 for 2 – 4 days. You then start at around 400 – 450 PPM and let the plant grow again and repeat the steps.
- You will find that the root ball becomes very large. You can trim off a little of the pulp each time you change the nutrient solution.
- The air pump must run 24 hours a day.
- Light cycle that works is 18/6 and 12/12 during fruiting
- If you have problems with the flowers not setting fruit, it could be:
– Low humidity
– Little air circulation
– Temperature too high (30+)
- Large leap between day and night temperature
- If something were to go wrong, you would see it quickly on the plant. Check all measurements to find the error.