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Frequently Asked Questions―Hydroponic Systems

Hydroponics is becoming increasingly popular among commercial and hobby growers for many reasons. Simply put, hydroponics is growing plants without soil. As long as there are nutrients in the water supply, soil is not essential for plant growth. Since this discovery in the 19th century, hydroponic growing has evolved into different types, with many benefits over traditional, soil-based cultivation. With the right setup, hydroponic growing is a cost-effective method of producing high-quality crops with maximum yields. Since this form of growing is becoming so popular, many of our customers have had questions on how to get started, and what they need to succeed. Here is a list of some of the more common questions we’ve had.

General Questions

1. What is the simplest system to start out with?

Tomatoes perlite dutch buckets.Dutch buckets are very easy to start with because you don’t have to worry about recirculating the water. Also, with a Dutch bucket system you can start off small and expand from there. With NFT channels, the channels themselves can be a bit difficult to handle. If you’re just starting out and have a small space, we recommend Dutch buckets, otherwise NFT channels will work well.

2. What is the difference between Dutch buckets and NFT?

In a Dutch bucket system, plants are grown in a media, like perlite, and a nutrient solution is provided to them from a drip system that is run on a timer. Water is not supplied continuously and it is not recirculated in this type of system. Any unused water is drained away. In nutrient film technique, or NFT, plants are grown in a channel. The channels are set up to create a slight slope towards one end. The water is usually recirculated and a nutrient solution continuously runs through these channels bathing the roots.

3. How deep is the liquid nutrient flow through the channel in hydroponic trays?

Lettuce in NFT channels.In the channels, the water is usually about 1/8″ deep. A better way to measure is by flow rate. You want the water to flow at a rate of four cups per minute. To measure the flow rate, run the system, hold a measuring cup at the end and time for one minute. Adjust the system to increase or decrease flow based on your results.

4. Are there ever problems with roots clogging up the channels?

Not that we have seen. Because you are constantly running a stream of nutrients over the roots, they don’t need to spread out to seek the nutrients they need.

5. How do you prevent the Dutch bucket drain hole from clogging up?

You can use a piece of screening, fine mesh, shade cloth, weed mat or a geotextile fabric—anything that will allow the water to still flow through without a problem.

6. What are the problems with recirculating water in Dutch bucket systems?

You can set up a system to recirculate the water, but it is more involved. There is much more plumbing and testing that needs to be done. You would need to collect the runoff from the system and the water would need to be tested for nutrients. Each time the water runs through the system you will end up with different nutrient deficiencies based on what the plants absorbed. Once the water is adjusted to the proper nutrient levels, it can be recirculated back to the reservoir tank and run through the system again.

7. Can you use NFT channels for vine crops?

Pole beans growing from NFT channels.Yes. We recommend using the GT70 channels, since they are wider and deeper than other channels. They provide enough aeration for vine crops like tomatoes, cucumbers and squash.

8. What are the lengths of your NFT channels?

Our channels come in 10, 12 and 20 foot lengths. We also have joiners that allow you to extend the lengths or you can cut the channels to fit the size needed for your application. We recommend using a saw with a fine blade when you cut the channels. You can also cut the lids to fit any system size you want. If you want us to make custom channels for you (outside of the stock lengths), you must order a set minimum.

9. What does NSF certified mean?

NSF stands for the National Sanitation Foundation. Certified means that this system is made with food-grade recycled vinyl.

10. Can you grow different plants in the same channel at the same time?

Hypothetically yes, however each type of plant has their own nutritional needs, so it will be difficult to regulate the proper mix of nutrients. We don’t recommend this method unless you’re an experienced grower.

11.Can the systems be maintained without electricity? Can they be run by gravity only?

You could probably do this by putting the channels on a slope, but keep in mind you still need a way to pump the water through the channels. If running the pumps through another energy source such as solar or battery power is an option, then you can. Otherwise you will need electricity to move the water through the channels.

12. Does the nutrient water flow continuously?

In the NFT systems, the nutrient water flows continuously at a rate of approximately four cups per minute. When you first get started, the easiest way to measure the rate of flow is to hold a measuring cup at the end of the channel, turn the system on and see how much water you accumulate over one minute. The water does not flow continuously through the Dutch bucket systems; those systems run on a timer. Depending on what your crop is, you’re going to find that the timing is different. It can also be dependent on the temperature of the greenhouse and how quickly the plants are transpiring.

13. Do we have to drill the holes in the lids?

Lettuce growing from NFT channel.That is up to you. We offer the lids with no holes if you want to drill them yourself or we offer predrilled lids. If you decide that you want to grow something that requires larger spacing than what we provide, that is no problem. You can order the lids without predrilled holes.

Hydroponic Growing

1. Are there special seeds for hydroponics?

No, you can use almost any kind of seeds you want, as long as they are clean. If you are going to grow tomatoes, we would recommend using an indeterminate variety. That way the plant will keep producing flowers as long as you are growing.

2. What is the optimal temperature and humidity level for hydroponics?

You want to keep your water temperature between 68°F and 70°F. This is the range that will make the nutrients most readily available to the plants. Humidity is usually around 40% to 60%, but it depends on what you’re growing.

3. What is the optimum pH for hydroponics?

The optimum pH for plants is somewhere between 5.8 and 6.2. Any higher or lower pH can prevent nutrients from reaching the plants causing nutrient lockout. You may see signs of plant stress and mineral deficiencies, which can result in yellowing of the leaves, among other symptoms. It is important to maintain a proper pH level so the plants end up healthy and marketable.

4. Does growing hydroponically affect the taste or flavor of what is grown?

Lettuce growing in GT50 NFT channels.No, however, there have been studies done on hydroponic tomatoes showing that the tomatoes actually taste better than soil-grown varieties.

5. Can root crops be grown hydroponically?

Yes they can, however, as a beginner they may be quite challenging. Some more experienced growers do grow root crops hydroponically, but it is not something you should tackle unless you have experience.

6. How long will a single plant continue to produce before having to replace the plant?

Just like everything else, plants have a life expectancy. It depends on the plant. For instance, if you’re growing tomatoes that are either determinate or indeterminate varieties, once they stop producing, they need to be replaced.

7. What material is used to hold plants vertically and solidly in the channel?

That’s your choice. You can use rockwool, or we also offer something called Sure to Grow® which is a recycled plastic that is chemically inert and pH neutral. Both are good options; you just need something solid to hold the roots so they can grow out into the nutrient solution.

8. What lighting is best?

It depends on what you’re growing. The best thing to do is find out what the footcandle requirements are for the crop you’re growing and utilize that as a starting point.

9. Do you need to be concerned with any of the problems other large-scale growers have seen such as outbreaks of bacteria or disease?

Large scale hydroponic operation.Yes, there are problems that can arise in hydroponic growing. One of the things with hydroponics that is very important is the environment. You need to keep everything as clean as possible. You don’t want to have an outbreak in your system if you can help it. We recommend that you clean your channels on a regular basis with a mild bleach solution. Without soil, you won’t run into problems with soil-borne diseases. However that’s not to say you won’t run into problems with botrytis or insects. If you’re growing outside and using side or curtain ventilation, you need to have some kind of insect barrier to prevent insects from getting into your plants.

Nutrients & Pollination

1. How do you test for proper nutrient levels?

Hydroponic nutrient management system.pH levels can be tested to determine if the nutrients are being absorbed by the plants. It is best to use an electrical conductivity (EC) or a total dissolved solids (TDS) meter on a regular basis. In our system, we recommend placing the meter directly on the outside of the tank and recording your measurements on a daily basis. This will tell you whether you need to add more nutrient solution or more water and at what ratio into the channel. Keep in mind that ratios are crop specific.

2. In general, how often does the fertilizer solution have to be replaced in a NFT system?

It’s hard to say. Not only is it crop dependent, but it also depends on the size of the system you are running.

3. What is the best way to recycle the used nutrient solution when you need to change it?

You can use it on your house or garden plants. Most of the nutrients will already have been used by the plants in the system, so expect the nutrient solution to be less concentrated than when you first used it.

4. How do you pollinate crops if they require it?

You can either pollinate by hand every other day during the necessary 4 to 6 day period by taking pollen from the male part of the flower to the female part or you can bring in beneficials. Bees or wasps that pollinate the flowers are examples of beneficials.

5. Has anyone tried to use a bee hive in their greenhouse with hydroponics to help with pollination?

Yes, you can actually rent a bee hive for this purpose. They will send it to you by mail. Once the hive arrives, release the bees in the greenhouse. When they’re done, they will go back into the hive and you can mail it back. If you don’t want to hand pollinate or if you have a very large system, you can bring in bees without a problem.

Is there an important question we missed? Let us know and we will do our best to find the answer.

19 Comments Post a comment
  1. Paul Victor #

    Is it necessary to have grow lights in a greenhouse?
    Is there a way to reduce humidity cost effectively in a greenhouse if you live in a hot and humid climate?
    Thank you for a great article.

    July 24, 2012
    • Hi Paul,
      Thank you for your questions. The necessity for grow lights in your greenhouse depends on what you are growing and the time of the year. For instance, if you are trying to grow tomatoes in December you would need to have lights to lengthen the day light so the plants will produce flowers and fruit. Lights for tomatoes in July are not needed.

      To reduce humidity, hook an exhaust fan or circulation fans to a dehumidistat, that way when it’s too humid, the fans will turn on and move the air.

      July 25, 2012
  2. nadavu #

    Reblogged this on

    August 3, 2012
  3. Grace #

    Hello, I am on a robotics team for my high school and I was wondering about the flow rate of water supply. What do you recommend the rate of the water flow is so that the water can flow efficiently but now too rapid that it causes complications? We are not planning on doing a drip system but instead a current system which the water flows through and recirculates through the system. Everyone on my team is new in the hydroponics world but we are excited to know as much as we can so we can create an efficient hydroponic system that runs on a flowchart based software. 🙂

    December 1, 2013
    • Hi Grace,

      Thank you for your question. I am glad that your team is getting involved with hydroponics!

      There are a number of factors that go into determining the flow rate for your hydroponic system. It depends on what you are growing, the life stage of the plant and the environment in which it is grown. The best thing to do is some trial and error to see under what works best for your set up.

      The flow should be gentle and, depending on your channel depth, no more than 1/8″ deep. If the nutrient solution flows too quickly, the roots will not be able to absorb the nutrients effectively. Try a flow rate of about 4 cups per minute and adjust as needed from there.

      I hope that helps. Good luck!

      December 4, 2013
  4. roger #

    I have a free source of 2 gallon buckets. Is this too small for growing tomatoes?

    June 5, 2014
    • Hi Roger,

      Overall, I would not recommend it. It’s unlikely you will get good production. Tomato plants have very large root systems and growing in a container that is too small can result in issues with moisture retention, oxygenation and nutrient uptake.

      The smallest container we recommend is our 11 liter PolyMax Dutch Bucket (just shy of 3 gallons).

      The minimum size we recommend for growing in soil is 5 gallons.

      June 9, 2014
  5. Roxana #

    How do measure how much water must go in the nutrienttank or how big your watertank must be ?

    July 31, 2014
  6. Robert Frayer #

    I have a question:
    I am interested in doing Dutch bucket hydro tomatoes next year outdoors. How would I go about keeping rain water out of my nutrients? I live in Mid-Michigan USA

    August 13, 2015
  7. does the root system of plant affect the growth pattern of the plant in case of continuos solution hydroponic proess

    October 9, 2015
    • With hydroponics, the size of the root system should not affect the growth pattern of the plant. However, you will need to consider the amount of root space required for healthy growth and plan your system accordingly. If you have a crop with a large root system (tomatoes for example) you will need a hydroponic system that offers abundant space for root growth (Dutch Buckets or deep NFT channels). If you have a crop with a small root system (lettuce) you will be able to produce in a shallow NFT channel. Attempting to grow a crop with a large root system in a shallow NFT channel will result in stunted growth and the crop will not thrive. If you have questions regarding what systems are best for specific crops, please give us a call at 1.800.476.9715 to speak with a Hydroponic Specialist.

      October 15, 2015
  8. If my channel is 10m long. What must the spacing measurement of the support brackets be.

    June 8, 2016
    • For a channel that is 48′ long, we recommend spacing of support brackets at 66″ on center. We would suggest spacing between 45″-55″ for support posts. If you would like to speak further about your system and develop a precise plan designed around your specific needs, please contact a Hydroponic Specialist at 800.476.9715.

      June 20, 2016
  9. Peter Dowdall #

    I have a Dutch bucket system, the water flow goes on top of my clay balls ,I have noticed that I am getting algae signs on the top, will this cause problems, I am having tip dieback problems on tomatoes! Can you help?
    Thank you,
    Kind regards
    Peter Dowdall

    July 3, 2017
    • Hi Peter,

      Signs of algae on top of the growing media is no cause for alarm. If there is large amounts of algae, this may be an issue, however, some algae growth is normal in these types of systems. As for the tip dieback, there could be some issues with your nutrition. You may want to look at your ratios or look into whether or not your plants are receiving the proper amounts of nutrition and water throughout the entire crop. There could be a clog in the dripper stake, slowing the nutrient rich water flow, or the dripper stake may just not be inserted in an ideal location on the grow blocks. This is just what we can think to recommend at this time, however, if you would like additional assistance with this matter, we recommend contacting a Hydroponics Specialist by phone at 800-476-9715. We hope to speak with you soon.

      Thank you.

      July 5, 2017
      • Peter Dowdall #

        Hi. Thank you very much for your advice.
        I will contact the expert for other info:
        I will act on your advice and give you
        feedback .
        kind regards
        Peter Dowdall.

        July 6, 2017
  10. lynnthet #

    hi, i am doing a project about hydroponic system. but i don’t know how much flow rate is suitable for my lettuce system.If can you tell me about flow rate and how to calculate them?please

    August 4, 2017
    • We recommend a flow rate of about four cups per minute. To measure the flow rate, run the system, hold a measuring cup at the end and time for one minute. Adjust the system to increase or decrease flow based on your results.

      August 4, 2017

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