Short answer: both are complete three-part nutrients that grow good Kratky crops when mixed correctly. MasterBlend is three dry powders weighed in grams, which makes it cheap per gallon for growers mixing a lot. General Hydroponics Flora is three liquids measured in milliliters, which is easier for small batches. The right one depends on how much you mix and whether you own a scale or a syringe.
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Side by side
| MasterBlend 4-18-38 kit | General Hydroponics FloraSeries | |
|---|---|---|
| Form | Three dry powders | Three liquid concentrates |
| Parts | 4-18-38, magnesium sulfate (Epsom salt), calcium nitrate | FloraMicro, FloraGro (2-1-6), FloraBloom |
| Where calcium comes from | Calcium nitrate | FloraMicro |
| Mixing order | 4-18-38, then magnesium sulfate, then calcium nitrate | FloraMicro first in fresh water, then Gro and Bloom |
| Measured with | A gram scale | A syringe or measuring cup in mL |
| Rates | One rate: 2.4 g, 1.5 g and 2.4 g per gallon; half for seedlings | Feed charts in mL per gallon that change by growth stage |
| Adjusting for crop | Same recipe; sold as a tomato and vegetable formula | More Gro for leafy growth, more Bloom for flowering and fruit |
MasterBlend figures are from Masterblend's mixing sheet; Flora details are from General Hydroponics' product pages.
Measuring: grams or milliliters
This is the difference I would decide on. MasterBlend's per-gallon rates are small, and per quart they fall below a gram (0.6 g, 0.38 g and 0.6 g). A kitchen scale that reads in whole grams cannot do that. With MasterBlend I mix a gallon or more at a time on a scale that reads to 0.01 g.
Liquids are easier to measure in small amounts. A 10 mL syringe with clear markings is accurate enough for a single jar, which is why liquids suit growers with only a few containers. The method is in how to measure nutrient doses for mason jars.
Mixing
Both have an order, and both orders exist for the same reason: calcium and the sulfate and phosphate parts react when they meet in concentrated form. With MasterBlend, each powder goes into the full volume of water and dissolves before the next. With Flora, General Hydroponics says to add FloraMicro to fresh water first. Either way, never combine the concentrates before they are diluted; why two-part nutrients come in two bottles explains it.
Working out cost per gallon
Prices change too often to print, so here is how I compare them. Divide the price of a package by the gallons of finished solution it makes.
- MasterBlend: a pound of 4-18-38 is 453.6 g. At 2.4 g per gallon that makes about 189 gallons. Calcium nitrate is used at the same rate, and Epsom salt at 1.5 g, so a pound of Epsom salt makes about 302 gallons. The 4-18-38 usually runs out first.
- FloraSeries: take the bottle size in milliliters and divide by the mL per gallon from the feed chart for your crop and stage. Do it for each bottle; the one used fastest sets the cost.
For a grower filling a few quart jars a season, the difference is small. For someone filling totes every month, it is worth the five minutes of arithmetic.
Which I would pick
- A few jars of greens, no scale: FloraSeries with a syringe.
- Many jars or totes: MasterBlend, mixed by the gallon.
- Tomatoes or peppers in large containers: either; MasterBlend 4-18-38 is sold as a tomato formula, and Flora lets you raise Bloom for fruiting.
Whichever you use, measure the finished batch if you can. Oklahoma State University Extension gives 1.2 to 1.8 mS/cm for lettuce, and the EC and PPM guide has other crops.
Switching from one to the other
If you change systems, change between crops, not in the middle of one. I finish the crop, empty and clean the container, and mix the new product from its own instructions. I do not carry over any habit from the old one: a dose that gave 1.5 mS/cm with one system says nothing about the other. Measure the first batch of the new product, write the reading down with the amounts used, and treat that as your new starting point. If you do not have a meter, follow the new maker's rate exactly for the first crop and watch the plants before adjusting anything. The same goes for pH: test the new batch rather than assuming it behaves like the last one.
Where to buy
Quick questions
Can I mix MasterBlend and Flora together?
I would not. Each system is balanced as a set; combining them gives a solution neither maker designed, and you lose the ability to follow either set of instructions.
Does one change pH more than the other?
Both depend heavily on your water. Mix, wait, then test; the targets are in the pH guide.
Related guide: choosing a nutrient for Kratky hydroponics. Also see best nutrients for the Kratky method.
Sources
- Masterblend International. 4-18-38 Tomato Formula: Masterblend Mixing Instructions.
- Masterblend International. Tomato & Vegetable Formula 4-18-38.
- General Hydroponics. FloraMicro Calcium and Chelated Micronutrient Base.
- General Hydroponics. FloraGro Vegetative Growth Base Nutrient.
- General Hydroponics. FloraBloom Flowering and Fruiting Base Nutrient.
- Dunn, B. and Singh, H. Oklahoma State University Extension. Electrical Conductivity and pH Guide for Hydroponics (HLA-6722).