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MasterBlend & General Hydroponics ppm chart
Two of the most-searched hydroponic nutrient lines are MasterBlend (a three-part dry mix) and General Hydroponics Flora series (a three-part liquid). Both ship a "feed chart," but the number that matters is the ppm/EC you measure in the reservoir — which depends on your dose, your water, and your crop's target. Here's how to mix each and read it against the per-crop ppm targets.
MasterBlend mixing ratio (per US gallon)
The widely-used MasterBlend tomato formula is a 2:2:1 ratio by weight, added as three separate parts so calcium and sulfate don't precipitate:
| Part | Per gallon | Role |
|---|---|---|
| MasterBlend 4-18-38 | 2.4 g | N-P-K + micros |
| Calcium nitrate 15.5-0-0 | 2.4 g | Calcium + nitrate N |
| Epsom salt (MgSO₄) | 1.2 g | Magnesium + sulfur |
Mix order matters: dissolve MasterBlend fully, then Epsom salt, then calcium nitrate last — never combine calcium nitrate and the sulfate in concentrated form. This full-strength mix lands in the general vegetable range; dilute it for seedlings and leafy greens, or run full for fruiting tomato and pepper. Confirm the exact EC against your crop's stage target.
General Hydroponics Flora series
GH's three liquids — FloraMicro, FloraGro, FloraBloom — are dosed in mL per gallon and shifted by stage (more Grow early, more Bloom at flower). GH publishes the per-stage mL schedule on the bottle and online. Because it's a liquid concentrate, the same principle applies: the feed chart is a starting dose, not a ppm guarantee. Always add Micro first, stir, then Gro, then Bloom, to avoid nutrient lockout in the concentrate.
The feed chart assumes zero-ppm water. Your tap or well water already carries dissolved solids (often 100–300 ppm). Subtract your source-water EC from the target, or you'll consistently overshoot. Measure the water before you add anything.
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Gear this guide uses
Turning a brand ratio into a reliable ppm means weighing parts and reading the result.
- Weigh dry parts to the tenth of a gram on a 0.1 g scale.
- Buy the parts: MasterBlend 4-18-38 kit or General Hydroponics Flora series.
- Verify the mix with an EC / ppm meter.
Crop does the brand math
Pick MasterBlend, Jack's, or General Hydroponics and Crop converts your crop-and-stage ppm target into exact part weights or mL for your reservoir volume — accounting for source-water ppm. Pay once, no subscription, works offline.
FAQ
What is the MasterBlend tomato formula ratio?
2.4 g MasterBlend 4-18-38, 2.4 g calcium nitrate, and 1.2 g Epsom salt per US gallon — a 2:2:1 ratio by weight, mixed as three separate parts.
What ppm does the General Hydroponics Flora series make?
Whatever you dose it to — GH gives a mL-per-gallon schedule by stage; measure the resulting ppm/EC and match it to your crop target.
Should I trust the ppm on the feed chart?
As a start, yes; then verify with a meter. Feed charts assume zero-ppm water, so your source water pushes the real reading higher.
Sources
- MasterBlend and General Hydroponics product label directions (manufacturer mixing ratios)
- Penn State Extension — Hydroponics nutrient solutions (target EC/ppm the mix should hit)
- Cornell CEA (Mattson & Lieth) — crop nutrient targets
Ratios are the manufacturers'; the crop targets they should meet come from university extension research. Verify with your own meter.