Keep stock concentrates clean with 1 mL of regular unscented bleach (6–8.25% sodium hypochlorite) per gallon of concentrate, added to each container separately, and store them in dark or opaque containers. Re-dose the bleach monthly if they sit. Floaters get strained out; crystals get mixed for 5 to 10 minutes. Dry powders and RunClean don't expire.
Keep them clean
- Bleach: 1 mL per gallon of concentrate. A 5-gallon tank takes 5 mL, a 50-gallon drum 50 mL. The 0.2 mL per gallon rate is for finished feed, not stock.
- Never mix concentrates. Never combine concentrated A and B, and never premix concentrated bleach with RunClean or pH up.
- RunClean tanks get no bleach. If a stock has RunClean in it, skip the bleach in that tank.
- Dark or opaque containers, kept covered.
The full reservoir routine is in Our Bleach Routine.
Floaters
If you already see floaters, add the bleach at 1 mL per gallon and strain them out through cheesecloth or a coffee filter. The concentrate is still fine to use. If you can't tell what went into a tank, mix a fresh one instead of guessing.
Crystals and settled powder
Crystals mean it needs more mixing. Break up whatever has settled and mix it for 5 or 10 minutes, not a quick stir. We dissolve stock with a drill-mounted mixing bit, then keep a small wavemaker or mixing pump in the tank.
- Fill the tank about half to 60% of the way with water.
- Add the powder to the water while mixing. Too little water, or water poured onto the powder, can leave a hard mass on the bottom.
- Mix until nothing is left on the bottom.
- Top up to the marked final volume.
Cake is the slowest to dissolve, especially in cold water; we've used 90 °F water for Cake stock (more in Cake: pH, EC, Concentrate and DWC). Don't send undissolved chunks through your drippers.
If you added extra water to rescue a batch, the stock is now weaker than the recipe, and 30 mL per gallon won't give chart strength. Work out the new strength from the powder weight and final volume, or remix. Recipes and injector rates are in Mixing CropSalt Stock Tanks and Concentrates Correctly.
How long things keep
| Product | How long it keeps |
|---|---|
| Dry powders | They don't expire as long as they stay dry. Hard or clumpy Part B is fine; powder wet enough to show liquid drops is not. |
| RunClean | Doesn't go bad. |
| Stock concentrate | We've kept stock tanks in use without seeing them go bad. Keep them covered and dark, keep a wavemaker running after the initial mix, and re-dose the bleach monthly if they sit. |
| Mixed feed | Mix a batch you'll use within about a week, with a sterilizer in it (sterile soluble systems). |
Keep the powder dry
Part B pulls moisture from the air. Open the bag only while you weigh, clear the powder out of the zipper, push the air out and seal it. If you open it often, keep it inside a second sealed bag. If you move powder to another container, keep the label with it.
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