# Stock solution

> A stock solution is a concentrated nutrient mix, often 100x or 200x final strength, diluted into the reservoir; calcium and sulfate/phosphate stocks must stay separate.

- Canonical: https://genetixbay.com/knowledge/glossary/stock-solution.html
- Also written: nutrient concentrate, stock tank, 100x stock
- Glossary category: Nutrients · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

A stock solution is a concentrated solution of one or more fertiliser salts, made at a fixed multiple of feeding strength, typically 100x or 200x. It is diluted into the reservoir or injected through a dosing system to give the final nutrient solution.

## In practice

Stocks make home-made feeds practical: weighing salts once for 10 litres of 100x stock covers 1,000 litres of feed, and [micronutrients](https://genetixbay.com/knowledge/glossary/micronutrient.md) that would need milligram weighing become millilitre doses. The rule is separation. Calcium salts go in tank A; [sulfates](https://genetixbay.com/knowledge/glossary/sulfate.md) and [phosphates](https://genetixbay.com/knowledge/glossary/phosphate.md) go in tank B; [iron chelate](https://genetixbay.com/knowledge/glossary/iron-chelate.md) usually goes in A. Solubility limits how strong a stock can be; [potassium sulfate](https://genetixbay.com/knowledge/glossary/potassium-sulfate.md) is the common [bottleneck](https://genetixbay.com/knowledge/glossary/genetic-bottleneck.md). Store stocks cool and dark, label them with recipe and date, and use acid-resistant containers if acid is included.

## Units and formula

For a stock at multiple M: grams of salt per litre of stock = target mg/L of element ÷ (element % × 10) × M.

## Don't confuse with

- **Stock plant**: a [mother plant](https://genetixbay.com/knowledge/glossary/mother-plant.md) kept for cuttings.
- **Working solution**: the diluted feed that reaches the roots.

## Related terms

[A/B nutrient](https://genetixbay.com/knowledge/glossary/a-b-nutrient.md), [Per-element dosing](https://genetixbay.com/knowledge/glossary/per-element-dosing.md), [ppm of an element](https://genetixbay.com/knowledge/glossary/elemental-ppm.md), [Calcium nitrate](https://genetixbay.com/knowledge/glossary/calcium-nitrate.md), [Micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md)

## Read more

- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)
- [Per-element feeding tricks: what growers adjust, stage by stage](https://genetixbay.com/knowledge/nutrients/per-element-tricks.md)

## Sources

1. Sonneveld C, Voogt W. 2009. Plant Nutrition of Greenhouse Crops. Springer. https://doi.org/10.1007/978-90-481-2532-6