Our Bleach Routine: How Much, When and in What Order

Add 0.2 mL of regular unscented bleach (6–8.25% sodium hypochlorite) per gallon of finished feed every time you mix a reservoir, then add it again every 4 days until you change the reservoir, dosed on the volume that's left. A 100-gallon tank takes 20 mL; with 50 gallons left on day 4, add 10 mL. It doesn't change your pH, and there's no need to aerate tap water first.

Bleach handles organic buildup. RunClean handles scale. They do different jobs, so a sterile soluble reservoir gets both.

How much to add

Dose on the gallons actually in the tank, not the size of the tank.

That's 0.2 mL, two tenths of a milliliter, not 2 mL. Use regular unscented bleach (6–8.25% sodium hypochlorite); skip scented, splashless and specialty formulas. Never use scented bleach.

When to add it

1. Fresh reservoir: 0.2 mL per gallon once the feed is mixed.
2. Every 4 days after that (day 4, day 8 …): 0.2 mL per gallon of what's left in the tank.
3. Keep that rhythm until you change the reservoir.

Mix a batch you'll use within about a week. Bleach won't make a three-week batch reliable.

The order: A, B, bleach, RunClean

Into a reservoir or an injector line, it goes Part A → Part B → bleach → RunClean. Let each one mix in before you add the next. Bleach and RunClean are fine together in the finished feed, but never premix any of them as concentrates.

Stock concentrates

Never mix concentrated bleach with RunClean — it can release chlorine gas. Concentrates get a different rate: 1 mL of bleach per gallon of concentrate, added to each container separately. A 5-gallon Veg A tank takes 5 mL, and so does the 5-gallon Veg B tank. If a stock tank has RunClean in it, that tank gets no bleach.

Store concentrates in dark or opaque containers and re-dose the bleach monthly if they sit. Floaters, crystals and storage are covered in Keeping Concentrates Clean.

When to skip it

Skip bleach if you're running beneficial microbes or Granular. A sterilizer works against the microbes, so pick one approach. Granular has organic components, and we run microbes with it, not bleach.

Shock the empty system between crops

Between crops, run plain bleach at 10 mL per gallon through the empty system with the plants disconnected. A 50-gallon system takes 500 mL. Flush it with clean water before you reconnect anything. Never mix the shock with RunClean, acids or ammonia.

For why we use plain bleach, what 0.2 mL per gallon actually adds and how it compares with HOCl products, see Why We Use Plain Bleach in Our Reservoirs.