Hydroponic Nutrients Guide


If you’ve come from my post on hydroponics for beginners, welcome!

If you haven’t, welcome anyways!

This post is designed to give you an overview of hydroponic nutrients – what they’re made of, what they do, and the different types.

What are Hydroponic Nutrients?

Because we are growing plants without soil, we miss out on a good deal of nutrients that soil contains. When mixed with water, hydroponic nutrients are designed to replace all of the macro and micro nutrients found within soil. So, exactly what makes up a bottle of nutrients?

The first thing you’ll notice when you browse through bottles of nutrients are three numbers printed on the front of every bottle. This is known as the N-P-K ratio, or Nitrogen/Phosphorus/Potassium ratio.

The NPK ratio tells you exactly how much of each macro nutrient the bottle contains. If a bottle says 9-9-9, this means that the solution contains 9% Nitrogen, 9% Phosphorus, and 9% Potassium. You might have noticed that this adds up to 27% – what’s in the other 73%? Typically, water, micro nutrients and other chelating agents make up the rest of the solution.

The NPK ratio will differ depending on what phase of growth the plant is in – but we’ll get to that later. First, let’s talk about what these different macro nutrients do for a plant’s growth.

What Do Plants Need to Grow?

Before we dig into hydroponic nutrients, it’s important to understand exactly what nutrients plants need in the first place. Just like animals, plants need certain elements to survive and thrive.

There are two types of nutrients they need: macronutrients and micronutrients.

By understanding each one of these macro and micro nutrients, you’ll be able to figure out what your specific plant needs as well as any problems that might arise from a deficiency or surplus in any of them.

Macro Nutrients

Nitrogen, Phosphorus, Potassium. These three nutrients are absorbed in the largest quantities by plants and are known as macro nutrients. They serve absolutely vital roles in a plant’s development.

Here’s what each of them do:

Nitrogen (N)

Without nitrogen, plants have no ability to produce leaves. It’s responsible for a lot of the core functions of a plant’s growth:

  • Leaf growth
  • Leaf color
  • Amino acid, proteins, nucleic acid, and chlorophyll synthesis

You can tell your plants have enough nitrogen when their leaves have a vibrant green color and their growth rate isn’t slow.

If your plants are suffering from a nitrogen deficiency, the first place you should look are the older leaves. They typically display the telltale signs of a nitrogen deficiency first: yellowing leaves.

Phosphorus (P)

Phosphorus is essential for proper synthesis of a plant’s DNA and RNA. It’s also necessary for the proper development of many parts of your plants:

  • Stems
  • Roots
  • Flowers
  • Seeds

As you might imagine, your plants will need more phosphorus as they reach their flowering stage, but it’s essential throughout the entire life cycle of your plants.

Phosphorus deficiencies will cause stems to be weak, leaf and root growth to slow down, and flowers and seeds to be either malformed or not develop at all.

Potassium (K)

The main role of potassium in a plant’s life is to synthesize both proteins and carbohydrates. It also plays a role in the development of flowers, roots, and stems to a smaller degree.

Micro Nutrients

Plants need more than the three macro nutrients to thrive. The following nine elements are known as micro nutrients, and are required in smaller quantities for a healthy plant.

Boron – Combined with Calcium, helps to form cell walls.

Calcium – Combined with Boron, helps to form cell walls.

Copper – Activates enzymes and is required for respiration and photosynthesis.

Iron – Used to form chlorophyll and in respiration of sugars for energy.

Magnesium – Catalyzes the growth process and makes oxygen during photosynthesis.

Sulfur – Synthesizes protein, helps with fruiting, seeding and water uptake. Also acts as an organic fungicide.

Zinc – Helps to form chlorophyll, along with assisting respiration and nitrogen metabolism.

Types of Hydroponic Nutrients

Nutrients typically come in two different varieties – powdered and liquid.

The powdered variety is generally harder to work with. It won’t dissolve fully into water and oftentimes doesn’t have added pH buffers.

Liquid varieties are much more popular and easy to use. They come highly concentrated, so it’s important not to spill any on your body or your plants. Other than that, they’re fairly easy to use. All you need to do is mix them thoroughly into water at the desired concentration, and you’re set. Most of them come with pH buffers, which means that you don’t have to balance the pH of your water yourself – the nutrients do it for you.

General Hydroponics Flora Grow, Bloom, Micro Combo Fertilizer set, 1 Quart (Pack of 3)
  • GH Flora Series is the original Building Block Nutrient...
  • Users can adjust mixtures to suit specific plant needs;...
  • Contains highly purified concentrates for maximum solubility
  • PH balanced for ease of use; NASA and Antarctic research...

The picture above is an example of a very basic liquid nutrient package. The General Hydroponics Flora Series of nutrients is the most-used hydroponic nutrient package in the entire world. It contains FloraGro, FloraMicro, and FloraBloom nutrients. As your plants grow through their lifecycle, you need to provide them with different ratios of nutrients. This is where the GH Flora Series really shines, as it makes it very easy for you to customize your nutrient mix. I believe it sells for around 20 bucks as well, which makes it a super cheap way to get into growing plants hydroponically.

If you want to go with the GH Flora Series, I’d suggest picking up their pH buffer and testing kit. It will help you adjust the pH of your nutrient solution so that it’s absolutely perfect for your plants.

Get Started!

Hopefully this article has shined some light on the potentially confusing world of nutrients for hydroponic systems. While there are hundreds of different brands and varieties out there, it’s best to keep it simple as a beginner. For this reason, I recommend starting out with:

This is all you’re going to need to feed your plants a balanced mix of nutrients that will help them grow as optimally as possible!

Ready for more?

Check out the next article in my Hydroponics From Scratch series – pH and Nutrient Availability!

The Green Thumbs Behind This Article:

Kevin Espiritu

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35 thoughts on “Hydroponic Nutrients Guide”

  1. Hi there .I’ve noticed that flora bloom and flora rippen ^which is supposed to be a plant finisher ^ are identical except for 1% more p and k .to me this don’t make sense could I use flora rippen in my 3 part mix to get more p and k .confused thankyou

  2. Kevin,

    I am new to hydroponic gardening, only one year of experimentation so far? I have found out that different plants need entirely different solutions of Nitrogen/Phosphorus/Potassium. Can you advise me on where I can find the proper ratio for different plants, such as, tomato vs cucumbers vs pepper plants vs beans vs yellow crooked neck squash?

    I am using a starter mix of 4-18-38, which is a tomato hydroponics nutrient fertilizer, mixed 8oz to 100 gal of water. How can I vary that for each plant type?


    • This is a great question Bob and one I don’t have an answer for on the site just yet. I’m making it a priority to get some ‘recipes’ for different plants up soon though!

  3. Someone please explain to me Nitrogen amount difference between
    flora grow 2-1-6
    flora micro 5-0-1

    why is there more N in micro?
    why is there even N in micro is there any special reason?


  4. Hi Kevin I have built an not hydroponic system in my greenhouse
    And I have grown tomatoes and melons in it this year for first time
    I have have plenty of crops and tomatoes ripend will but they tasted
    A bit tangy is there anything I could do next year to get sweeter
    Toms ? Thank

  5. Hi kevin,
    From India and just love to do gardining and find new ways Hydrophonic but it ia very new to me. For beginner pl let me know the basic to mix the solution although the required solution are not easily availaible so had to make myself so please help me to start…

    • Hi Robin,

      Hard to answer given that I don’t know what you’re growing. I suggest looking up the back of a General Hydroponics feeding schedule online and going off of that with your custom-mixed nutrients!

  6. Hey Kevin,
    From a newbie’s perspective, would you recommend 2-part nutrient solutions such as Canna Coco A + B for small systems? Thanks very much, and greatly appreciate your professional guides! Keep up the awesome work!

  7. I Kevin,
    Nice to meet you! Your work is remarkable! Is has led me to new adventures! Congrats on how you motivate us by sharing your knowledge on the subject. I must admit. I am quite new at this, but I’m really eager to start growing my own veggies. I have recently assembled “Eliooo” vertical garden system (made with ikea items). It was really fun to do this DIY ! 🙂 However, I’m now stuck on a Hydroponics Calendar system. I have bought general hydroponics nutrients, but I’m completely lost on which growing calendar to implement. I am thinking to grow some herbs to start with. Do you have any ideas?

    Kind Regards

    • Nice to meet you as well Guilherme! I’m not sure what you mean by ‘growing calendar’, but you might mean ‘feeding schedule’. If you are growing herbs that don’t flower, it’s best to start out with about 1/2 the recommended feeding schedule for seedlings, then move on to mild vegetative growth and then normal vegetative growth on the back of the bottle. I hope that helps and happy gardening!

      • Hi Kevin,

        Thank you for the prompt reply! 🙂 Really appreciate it!
        I’m starting the seedling in a germination station (Hydrofarm Ck64050 ) and later on I will transplanting them to the vertical garden. Should I be worried about the PPM and PH levels while the plants are in the germination station period? Should I apply nutrients, air supply (pump) as well?

        Kind regards and thank you in advance. 🙂

        • Chlorine is easily solved by just exposing water to air for 24 hrs. PPM and pH should be calibrated yes, but don’t need to worry about water hardiness :). I would use a very light nutrient solution and and air pump too!

          • Great tips! In my greenhouse I only added the general hydroponics root enhancer in the water. I thought it was only required to calibrate the PPM and PH after transplanting the plants to the vertical garden. Moreover, I have covered the greenhouse with a towel. Is this ok? I’m truly a beginner here. 😛 I have also been having some difficulty in buying the General Hydroponics GH1514 Ph Control Kit through amazong. It seems they don’t send it to where I live. Are there any other similar products you would recommend ?

  8. Dear Kevin,
    I’ll be teaching children Hydrophonics this summer and organic gardening. How safe and how organic are those general hydroponics nutrients you’ve recommended above? Plus would you be interested in coming to Barbados to see and help even if for a short period, this children’s project this summer.

  9. Thank u m. Kevin. for giving information about the hydropionic cultivation and pls let me know the best guide to do for tomato describe nutrition ratio and prevention of deseases

  10. I personally use X Nutrients, which comes in a similar 3 stage setup of grow/bloom/micro-nutrients. Works great for me but is a bit pricey. I don’t recall the size of the container but I think it’s about $20 a gallon for each. That will last almost a whole grow cycle but the bloom one goes the quickest, since it’s mainly bloom nutrients that are needed once the tomatoes etc start flowering.

    • I’ll have to check out X Nutrients. GH is a great starter for total beginners, but I agree that you’re going to want to experiment with different combinations, micronutrient solutions, etc once you’ve got a bit more experience, which it sounds like you have!

  11. Assuming we can’t get a hydroponics specific solution, will regular liquid solutions do?

    If so, what NPK contents are we looking for? The ones in the General Hydroponics look lower than any I’ve seen.

    • Hey Anthony,

      Regular liquid solutions are just fine and I actually use the General Hydroponics three part nutrient for most of my grows. Their line is a great – and cheap – way to get started growing. Their NPK values are low, but only because all three solutions (FloraGro, FloraMicro, FloraBloom) are used in unison to create the perfect nutrient blend for each phase of growing.

      Thanks for reading, and let me know if you have any other questions!

        • Thanks! Let me know when you do, I’d love to take a look. Also, let me know if there’s anything you’d like to see on the blog, I’m in the process of moving houses right now but once I’m settled in there’s going to be a lot more hydroponic tutorials, posts, etc!

  12. How often do you need to change the water & add nutrients to the system? I’m a great gardener in soil & trying to learn more about hydro dardening so any tips that you could give me would be helpful. Thank You for your time.
    James Hicks

    • Hi there James – I usually will refill the system every week, but I am a fan of making it as easy as it can be, so I tend to just fill it back up to the normal level instead of changing the entire system out. If you’re noticing a serious pH imbalance or too high/low parts per million of your nutrient solution, you might need to do a full swap just to get everything back to normal levels.

      Just adding what is needed is a great way to conserve water instead of dumping out 10 gallons a week 🙂

      • Yah I have a 55 gallon Rex and due to it large volume it easy to keep under control. I rarely switch out the whole thing, especially since I use RO water so it is timely and frankly wasteful. Just topping off the water and adding in some extra nutrients works great for me, about once a week I add some
        Nutes and a few gallons of water. Hasn’t done me wrong yet.

        If I had a smaller reservoir, I would change it out weekly since its harder to manage the appropriate levels when you only have 5 or 10 gallons of water to deal with. Adult tomatoes drink lots of water so it can be tough!

        • I really like the never drain strategy, wastes much less water and generally is more efficient. Only thing you have to deal with is exactly what you said – managing the water/nutrient ratio. I’ve only got 15-20gal reservoirs max, so this happens a lot to me. Water gets sucked up more than nutrients, PPM goes up and burn occurs so I’ve got to stay pretty vigilant when it comes to keeping my res in good shape.

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