Short answer
One complete base nutrient made for your medium, Cal-Mag only if your water or medium calls for it, a pH down, and meters for pH and EC. Bloom boosters, sugars and most additives are optional at best. Controlled cannabis trials found no gain above about 30–60 mg/L phosphorus or from doubling overall strength [1][2][3]. Supported.
Why
A complete base feed supplies all the essential elements. That is all the plant can use.
Phosphorus has a plateau. Several independent trials agree that once the root zone carries roughly 30–60 mg/L P, more does not raise yield or cannabinoids [1][3]. Extra phosphorus raised leachate P instead [1].
Strength has a plateau too. Doubling feed from 2 to 4 mS/cm in deep-flow hydro raised solution nutrients but not yield or cannabinoids [2].
Stacking products can backfire. Higher potassium supply lowered calcium and magnesium uptake in cannabis [4], which is what a PK booster on top of a complete base does.
House positions apply here: Cal-Mag need is driven by cultivar, RO water and coco, not by LEDs, and molasses feeds microbes, not the plant.
The numbers
| Item |
Need it? |
Notes |
| Complete base (soil one-part, or A and B for coco and hydro) |
Yes |
Matched to medium |
| pH down |
Yes, for coco and hydro |
Mineral acid |
| pH meter + buffers |
Yes, for coco and hydro |
Calibrate weekly |
| EC meter |
Yes |
Read in mS/cm |
| Cal-Mag |
Only with RO, soft water or coco |
Fill the gap to Ca 150–200, Mg 40–70 mg/L |
| Silica |
Optional |
Thin cannabis evidence |
| Bloom / PK booster |
No |
P plateau at ~30–60 mg/L |
| Molasses, sugars |
No |
Feeds microbes, not the plant |
What to do
- Pick your medium first.
- Buy one complete base made for it.
- Get a water report or measure your water's EC.
- Add Cal-Mag only if the numbers say so.
- Spend the rest on a good pH meter and fresh buffers.
Common mistakes
- Buying the whole ten-bottle line.
- Stacking boosters on a complete base.
- Running Cal-Mag with hard tap water.
- Skipping the meters to buy additives.
Cal-Mag is a supplement supplying calcium and magnesium, usually as nitrates; need depends on cultivar, water source (RO vs tap) and medium (coco), not on LED lighting.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.A bloom booster is a high-phosphorus, high-potassium additive sold for flowering; cannabis trials show a P plateau, so past moderate levels it adds cost and runoff, not yield.The root zone is the volume of medium or solution where a plant's roots live, including its water, air, temperature, pH, EC and microbes.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.mS/cm (millisiemens per centimetre) is the standard unit of EC for nutrient solutions; 1 mS/cm equals 1 dS/m and 1,000 µS/cm.RO water is water stripped of most dissolved salts by reverse osmosis; it has near-zero EC and little buffering, so pH moves easily and Ca and Mg must be added.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.An LED (light-emitting diode) grow light uses solid-state diodes to produce light; modern fixtures are the most efficient grow lights, at roughly 2.5–3 µmol/J.Molasses is a sugar-rich by-product of sugar refining added to soil feeds; its sugars feed soil microbes, not the plant, and do not sweeten buds.An A/B nutrient is a mineral feed split into two concentrates so that calcium (part A) is kept apart from sulfate and phosphate (part B), which would precipitate together.A pH meter measures solution pH with a glass electrode whose voltage changes with hydrogen ion activity; it needs regular calibration and a moist probe.An EC meter measures how well a solution conducts electricity, giving nutrient strength in mS/cm or as ppm via a conversion factor.The reproductive phase of the cannabis life cycle, from the switch to flowering until harvest, during which the plant stretches, builds buds and ripens resin.Tap water is municipal or well water used for irrigation; its EC, alkalinity, hardness, sodium and disinfectant vary widely, so it should be tested before use.
