Kratky Hydroponic Nutrients
Kratky fertilizer made for passive hydroponics. Mix once and grow lettuce, herbs, and greens with the kratky method no pumps, no fuss.
Mix it into the reservoir at setup as directed for a straightforward passive-hydroponic routine with no separate soil feeding step.
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Kratky Hydroponic Nutrients with a complete 4-3-6 NPK plus iron and full micros — made for the Kratky method, the passive way to grow plants in water with no pump, no electricity, and almost no maintenance. Because a Kratky jar is filled once and left alone, the nutrients have to be complete and stable from the start, feeding leafy greens and herbs straight through to harvest from a single reservoir.
How to Use Kratky Hydroponic Nutrients
| Method | Amount | How Often |
|---|---|---|
| Kratky hydroponic system | 5 mL (1/2 tsp) per quart of feedwater | Mix once at setup; add more only mid-cycle when topping up water |
Shake well before using. Mix into your Kratky feedwater at setup and otherwise leave it alone — the Kratky method works best with few water adjustments, so only add more fertilizer mid-cycle when you top up the water.
What's Inside
The 4-3-6 ratio is a complete, potassium-led formula designed to stand alone, which is exactly what the Kratky method needs — you fill the reservoir once and the plant lives off it, so the feed has to carry everything with no soil to fall back on. The 4% nitrogen supports leaf growth, the 3% phosphate builds roots, and the 6% potash backs vigor and any fruiting. The nitrogen is split between nitrate, absorbed directly, and a smaller ammoniacal and urea fraction for steadier release over the grow, which suits a system that isn't refreshed often.
Beyond NPK: sea kelp (Ascophyllum nodosum) for natural growth compounds, plus 1.0% calcium and 0.5% magnesium and a full micronutrient package — iron, sulfur, manganese, zinc, boron, and copper. In a passive system with no circulation, a complete micro package matters even more, since the plant can't be easily corrected once it's growing: iron prevents new-growth yellowing, and calcium and magnesium head off the tip-burn that shows up fast in water culture. Shake the bottle before dosing so the full blend goes in evenly.
Made For
Built for the Kratky passive hydroponic method — lettuce, leafy greens, and herbs grown in mason jars, buckets, and tubs without pumps or air stones — ideal for countertop and windowsill growing and first-time hydroponic gardeners.
Problems It Solves
- New growth yellowing in a passive Kratky jar
- Tip burn or interveinal yellowing on greens
- Weak, slow growth in a no-pump reservoir
- Plants stalling because the water lacks trace minerals
FAQs
How much nutrient do I add to a Kratky jar?
Add 5 mL (about 1 teaspoon) per quart of feedwater, mixed in at setup. The Kratky method works best with minimal fiddling, so once the jar is filled and the plant is growing, leave the reservoir alone — only add more fertilizer mid-cycle if you top up the water as the level drops. Shake the bottle well before measuring so the full blend is evenly mixed. Scale the amount to your container's water volume in quarts.
How is the Kratky method different from other hydroponics?
Kratky is passive — no pump, no air stone, no electricity. You fill a container with nutrient water, suspend the plant so its roots reach the water, and as the plant drinks, the water level drops and leaves an air gap that supplies oxygen to the upper roots. It's the simplest hydroponic method, great for leafy greens and beginners. The trade-off is you can't easily adjust the reservoir mid-grow, which is why a complete, stable nutrient mix matters so much.
Do I need to change or top up the water?
For quick crops like lettuce, a properly sized Kratky jar is often filled once and harvested without topping up — the falling water level is part of how the method oxygenates the roots. For longer grows, you may top up the water as it gets low; when you do, add nutrients to the fresh water you're adding, not a full new dose. Avoid frequent adjustments — the method is designed to be left alone, and disturbing it too much works against it.
Why are my Kratky plants yellowing?
In a passive system, yellowing often means the reservoir is running low or the nutrient mix has been used up, since there's no circulation refreshing it. Check the water level and whether roots still reach the water. New-growth yellowing can also point to iron or a pH drift, since Kratky reservoirs aren't actively pH-managed. This complete blend supplies iron and micros, but for longer grows, a basic pH check and a nutrient top-up when you add water keep plants green.
When will I see results?
Leafy greens and herbs grow quickly in a working Kratky setup, often showing visible new growth within a week or two. Because the system is passive, results depend on getting the initial fill right — enough nutrients, the roots reaching the water, and decent light. Existing damaged leaves won't recover, so you're feeding new growth. A well-set-up jar can take lettuce from seedling to harvest on largely one reservoir.
Related Products
Hydroponic Nutrients Hydroponic Plant Food Herbs and Leafy Greens Plant Food