AgSil 16h Unavailable? Here’s How to Use AgSil 25 Instead
AgSil 16h Shortage: Your Best Replacement Options
AgSil 16h is temporarily unavailable due to a raw material supply issue at Certis, the manufacturer. It is expected to return to availability in late June 2026. In the meantime, two proven potassium silicate alternatives are in stock and ready to ship from Custom Hydro:
- Pro Powders Silica Pro — Dry potassium silicate powder; the closest direct replacement for AgSil 16h
- AgSil 25 — Liquid potassium silicate; ideal for fertigation and hydroponic systems
Option 1: Pro Powders Silica Pro (Closest Direct Replacement)
Pro Powders Silica Pro is a dry potassium silicate powder — the same format as AgSil 16h — making it the easiest drop-in replacement for growers already using AgSil 16h in their programs.
Why Choose Pro Powders Silica Pro?
- Same dry format — No changes to your mixing or application equipment
- Same application rate — Use at 0.25 g per gallon for continuous feeding programs, just like AgSil 16h
- Potassium silicate source — Delivers soluble silicon and potassium directly to plant tissue
- Compatible with all application methods — Ground, aerial, fertigation, and hydroponic systems
Application Guidelines for Pro Powders Silica Pro
- Continuous feeding: 0.25 g per gallon of nutrient solution
- Add first — Always dilute potassium silicate into the working solution before adding other fertilizers
- pH note: Potassium silicate raises solution pH — adjust accordingly before adding other inputs
- Keep separate from concentrated fertilizer stock solutions to prevent precipitation
Option 2: AgSil 25 (Liquid Alternative)
AgSil 25 is a liquid potassium silicate providing 21% Silica (SiO2) and 8% Potassium (K2O) derived from potassium silicate. It is a 100% available source of silicon and potassium, making it highly effective for growers who prefer liquid inputs or run automated fertigation systems.
Why Choose AgSil 25?
- Liquid format — Easy to measure and inject; ideal for automated systems
- 21% SiO2 / 8% K2O — High-concentration formula for efficient silicon delivery
- Fully soluble — No residue; compatible with most foliar and fertigation programs
- Consistent silicon supply — Maintains steady low-level silicon in the root zone for continuous uptake
Suggested Dosage for AgSil 25
Add 0.47 mL (0.634 g) of AgSil 25 per gallon of nutrient solution. This delivers:
- 16.33 mg/L (ppm) Silicon (Si)
- 11 mg/L (ppm) Potassium (K)
This matches the silicon delivery of 0.25 g/gallon of AgSil 16h.
Application Methods for AgSil 25
- Fertigation & hydroponics: Add AgSil 25 as the first input into the working strength solution before other fertilizers
- Automated systems: Use a dedicated injector for AgSil 25 — first in the series — to ensure thorough mixing before other fertilizers are added
- Ground & aerial: Compatible with standard spray programs
Stock Solution Tips for Automated Systems
- Raise the pH of the starting solution above 11.3 with potassium hydroxide before adding AgSil 25 to prevent precipitation and cloudiness
- Use distilled or deionized water for concentrated stock solutions
- Keep stock solutions covered to prevent CO₂ absorption, which lowers pH and destabilizes the solution
- Use a mixing chamber after the silicon injector to ensure complete dilution before other fertilizers are introduced
Choosing Between the Two
| Feature | Pro Powders Silica Pro | AgSil 25 |
|---|---|---|
| Format | Dry powder | Liquid |
| Closest to AgSil 16h | ✅ Yes — same format | Liquid equivalent |
| Application rate | 0.25 g/gallon | 0.47 mL/gallon |
| Best for | Growers switching directly from AgSil 16h | Fertigation & automated systems |
| Automated injection | Dissolve first, then inject | Direct liquid injection |
Best Practices for Both Products
- Always add potassium silicate first — dilute into the working solution before any other fertilizers
- Keep concentrated solutions separate from other fertilizer concentrates to prevent precipitation, cloudiness, and polymerization
- Maintain pH above 11.3 in concentrated stock solutions for stability
- Supply a constant low level of soluble silicon in fertigation feeds for continuous root uptake
- Monitor and adjust injection rates based on plant requirements and growing conditions
In Stock & Ready to Ship
Both Pro Powders Silica Pro and AgSil 25 are available now from Custom Hydro. For smaller-scale needs, Sil-Matrix is also available in 2.5-gallon containers. AgSil 16h is expected to return in late June 2026 — we’ll update this page when it’s back in stock.
