Semi-Hydroponics Nutrient Additive Guide for LECA & Pon
Mixing a nutrient solution in semi-hydroponics is like cooking— you can make your recipe as simple or extravagant as you want it to be! While a basic nutrient solution provides your plants with the essential elements they need, incorporating specific additives can further enhance your plant’s growth, improve nutrient uptake, and protect against stressors like pests & diseases. In this article, we’ll discuss the different types of optional nutrient additives in semi-hydroponics and how you can use them to supercharge your plant’s growth in LECA or Pon!
New to semi-hydroponics? Don’t get overwhelmed! Read my Beginner’s Guide to Semi-Hydroponics first!
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One Word of Caution: Order Matters!
If you are going to take the leap and start using any or all of these additives to supercharge your semi-hydroponic nutrient solution, it is imperative that you add them in the order discussed on this page. Otherwise, you’ll render them ineffective at best, or cause nutrient lockout at worst!
What is Nutrient Lockout?
Nutrient Lockout occurs in semi-hydroponics when one or more nutrients in your solution create a chemical reaction that prevents your plants from absorbing those nutrients. This can lead to nutrient deficiency and eventually the death of your plant (over months or sometimes even years).
Causes of Nutrient Lockout:
Excess nutrients or not mixing them in the appropriate order
pH Levels that are severely too high or low
Build up of salts
Symptoms of Nutrient Lockout:
Yellowing leaves
Stunted growth
Leaf discoloration
Wilting
Plant death
How to Avoid Nutrient Lockout:
Always follow nutrient dosing instructions on the bottle
Mix your nutrients in the order discussed in this article
Check & adjust the pH level of your nutrient solution (discussed in Step 6)
1. Silica (Silicon)
★ Best For: Preventing leaf browning on highly variegated houseplants.
✔ Benefits of Silica:
Increases plant resistance to pests and diseases
Strengthens cell walls for strong stems and leaves
Improves drought tolerance
Enhances nutrient transport and efficiency of photosynthesis
How to Use Silica: When used, always add Silica to your nutrient solution first, as it will react with other elements if added later, causing nutrient lockout. Mix thoroughly. It is also recommended to let your solution set for 30 minutes before adding additional nutrients. The dosing for Silica Gold is 2-4mL per gallon.
My Experience with Silica: I’ve seen notable improvement in the leaves of my highly-variegated plants when using silica, but I must admit that the 30-minute waiting period dissuades me from reaching for it ever time I mix up my nutrient solution.
2. Calcium and Magnesium (Cal-Mag)
★ Best For: Supplementing essential nutrients lacking in your solution when using filtered, distilled, or reverse osmosis (RO) water.
✔ Benefits of Cal-Mag:
Strengthens cell walls for sturdier plants
Improves nutrient uptake and photosynthesis
Prevents common deficiencies like blossom-end rot in tomatoes
How to Use Cal-Mag: Mix Cal-Mag directly into your nutrient solution after silica but before your base nutrients to prevent nutrient lockout. The dosing for CALiMAGic is 5mL per gallon.
My Experience with Cal-Mag: Because I use tap water in my nutrient solution and Foliage Pro as my fertilizer (discussed next), I rarely have a need to supplement additional Calcium or Magnesium. But if you are starting from Distilled, Filtered, or Reverse Osmosis water, Cal-Mag is a must because its been completely stripped out of your solution.
3. Base Nutrients (One-Part, Two-Part, Three-Part Fertilizers)
As discussed in my Beginner’s Guide to Semi-Hydroponics, a complete hydroponic fertilizer is THE only ingredient you MUST add to your nutrient solution. But did you know that plants require different levels of nutrients depending on their growth stage and your goals as a plant parent? In general, a plant consumes more nitrogen during formative and vegetative stages (producing leaves, roots, & stems) and consumes more phosphorus, potassium, & magnesium as it flowers or fruits. These differences have led to 3 common fertilizer options: One-Part, Two-Part, & Three-Part Fertilizers.
What’s the difference?
✔ A "one-part" fertilizer is a single solution containing all the necessary macro & micro nutrients that plants need to thrive. It’s the simplest to use (no mixing multiple parts) and therefore the least customizable. Foliage Pro is an example of a One-Part Fertilizer.
How to Use One-Part Fertilizer: Simply mix your one-part fertilizer directly into your nutrient solution right after your Silica & Cal-Mag (if using either of those two additives). The dosing for Foliage Pro is 5 mL per gallon.
✔ A "two-part" fertilizer separates the main nutrients into two solutions: “A” (nitrogen-rich) and “B” (phosphorus/potassium-rich) that each need to be mixed into your nutrient solution separately (and never directly together). The multiple parts offers some customizability without adding too much complexity. Humboldt’s Secret Grow-Bloom Series is an example of a Two-Part Fertilizer.
How to Use Two-Part Fertilizer: After Silica & Cal-Mag, first mix Part A directly into your nutrient solution, followed by Part B. Dosing will depend on your plant’s growth stage and/or your preferences.
✔ A "three-part" fertilizer further divides the nutrients into three separate solutions: “Micro” (micronutrients), “Grow” (nitrogen-rich), & “Bloom” (potassium-rich). Again, each part needs to be mixed into your nutrient solution separately (and never directly together). Three separate parts allows for the most customization, but also the greatest number of steps. General Hydroponics’ Flora Series is an example of a Three-Part Fertilizer.
How to Use Three-Part Fertilizer: After Silica & Cal-Mag, mix “Micro” directly into your nutrient solution, followed by “Grow”, and then “Bloom” (in that order). Dosing will depend on your plant’s growth stage and/or your preferences.
My Experience with Fertilizers: Call me boring, but I have always preferred the simplicity of a plain old One-Part fertilizer like Foliage Pro!
4. Fulvic Acid & Humic Acid
★ Best For: Increasing the effectiveness of your base nutrients, making them easier for your houseplants to uptake.
✔ Benefits of Fulvic Acid & Humic Acid:
Fulvic Acids act as efficient nutrient carriers
Humic Acids promote healthy microbial activity and nutrient availability
How to Use Fulvic Acid & Humic Acid: Mix Fulvic Acid & Humic Acid directly into your nutrient solution after your base nutrients but before you pH balance your solution. The dosing for Mr. Fulvic is 1mL per gallon.
My Experience with Fulvic Acid & Humic Acid: Because I use a Rosmeric Acid product (discussed next) that also happens to contain Humic Acid, I usually skip this additive. But if you’re looking to get the most out of your fertilizer, I highly recommend it!
5. Rosemary Oil
★ Best For: Treating & preventing thrips, spider mites, fungus gnats, and root aphids.
✔ Benefits of Rosemary Oil:
Systemically controls most plant pests (thrips, spider mites, fungus gnats, root aphids) by allowing the plant to take up rosemeric acid in its cell walls, creating a barrier that deters and harms sap-sucking insects
Is the only systemic pest control product on the market that can be added directly to your water reservoir
How to Use Rosemary Oil: Mix rosemary oil directly into your nutrient solution after your base nutrients but before you pH balance. The product I recommend, SNS 209, also contains Humic Acid, so you may choose to use this in place of something like Mr. Fulvic. The dosing for SNS 209 is 7mL per gallon.
My Experience with Rosemary Oil: This is THE only systemic pesticide on the market that can be added directly to your semi hydro nutrient reservoir. I really love this stuff and use it every time I water to prevent plant pests.
6. pH Buffers
★ Best For: Preventing nutrient lockout in severe cases.
✔ Benefits of pH Buffers:
Prevent nutrient lockout from mistakes made in nutrient mixing
Ensure optimal nutrient uptake within the ideal pH range of 5.5-6.5
How to Use pH Buffers: Use a calibrated pH meter to measure the pH of your nutrient solution thus far. If the pH of your nutrient solution is higher than the ideal range, you’ll dilute pH down in a separate water cup and then slowly mix this dilution into your solution until the pH meter reports an acceptable reading. If your nutrient solution is lower than the ideal range, you’ll follow the same steps, except with pH Up.
My Experience with pH Buffers: You might be surprised to learn that despite all of my scary warnings & graphs about nutrient lockout, I rarely use pH Buffers. Why? Because I feel that the emphasis placed on pH levels in semi-hydroponics is usually overblown. If you’re mixing up a basic nutrient solution with tap water and fertilizer, you don’t need to test pH levels. I almost always use the same nutrient solution recipe, and every time the pH of that recipe has measured within a safe range (~7.0). However, this might not be true if you are mixing up an elaborate nutrient recipe, so in that scenario, I would recommend testing to ensure a safe pH level.
The effect of soil pH on nutrient availability.
Roques, Susie & Kendall, Sarah & Smith, K.A. & Newell Price, Paul & Berry, P.. (2013). Review of the non-NPKS nutrient requirements of UK cereals and oilseed rape.
7. Rooting Stimulants
★ Best For: Transitioning soil plants to a semi-hydroponic set-up.
✔ Benefits of Rooting Stimulants:
Reduces plant transplant shock
Promotes explosive root growth and branching
How to Use Rooting Stimulants: Mix rooting stimulant directly into your nutrient solution after pH balancing. The dosing for Rapid Start is 1mL per gallon and works EXTREMELY well.
My Experience with Rooting Stimulants: I find rooting stimulants are most effective when first transitioning a plant to semi-hydroponics. They’ve since become my secret weapon to successful semi-hydro transitions!
8. Hydrogen Peroxide
★ Best For: Fighting root rot and algae.
✔ Benefits of Hydrogen Peroxide:
Oxygenates your solution to combat bad bacteria
Eliminates build up and algae growth
Stimulates root growth and nutrient uptake
Removes chlorine
How to Use Hydrogen Peroxide: Mix 3mL of 3% solution of Hydrogen Peroxide directly into your nutrient solution after pH balancing but before any Beneficial Microbes.
My Experience with Hydrogen Peroxide: I love adding Hydrogen Peroxide to my nutrient solution, especially when I have a bad algae or root rot outbreak!
9. Beneficial Microbes
★ Best For: Boosting plant resistance to bacteria and diseases in the root zone.
✔ Benefits of Beneficial Microbes:
Decomposes organic matter (such as algae) to increase nutrient availability
Controls a variety of pathogens and fungal diseases that attack plant roots
How to Use Beneficial Microbes: Mix beneficial microbes into your nutrient solution as your very last step. This is because we don’t want to harm any of the living microbes, and it won’t alter the pH of your solution. The dosing for Hydroguard is 2mL per gallon.
My Experience with Beneficial Microbes: Although some people swear by beneficial microbes like Hydroguard, I personally find Hydrogen Peroxide to be much cheaper and more effective promoting root health (and fighting algae blooms).
My Personal Nutrient Solution Recipe
As mentioned before, I’m really lazy. Sometimes I just use Foliage Pro and call it a day. But, as of 2025, my preferred nutrient cocktail is the following:
1 Gallon Tap Water
5 mL Foliage Pro Fertilizer
7 mL SNS 209 (Rosemary Oil + Humic Acid)
1mL Rapid Start (Rooting Stimulant) for plants still transitioning from soil to LECA or Pon
3mL 3% Hydrogen Peroxide
I feel like this nutrient solution recipe incorporates a variety of added benefits for my plants without being overly complicated or expensive!
