How many gallons per hour flow do I need in a constant flow system using Grow-Cubes, if I have shelves feeding the plants on shelves below them?

Giving a watering recommendation is always difficult because it depends on variables such as the intensity of light you are using, how mature the plants are, etc. Please download the brochure “Watering and pH” from the brochure page for helpful hints. Also, I am concerned about using a constant flow system for two reasons: 

  1. Keeping the stone wool continuously saturated makes the plant’s roots “lazy”. So they will be weak because they don’t have to grow in order to get water.
  2. Watering into the night, when the lights are off, creates an environment conducive to the spread of diseases such as Pythium.

My recommendation is to water 2-3 times per day, but again depending on the light intensity and maturity of the plants. Bigger plants will of course need more water. You don’t want to keep the Grow-Cubes™ fully wet all the time- it’s good for them to just be slightly wet for most of the day. The best thing to do is to start with a low flow, such as 0.5 gph. For the first watering, let it drip through the entire 6 shelves, and measure the time it took to saturate all 6 shelves and get some drainage from the last shelf. If later in the day the Grow-Cubes feel like they are drying out, repeat the watering; but not as long as the first time (remember you don’t want to fully saturate the Grow-Cubes again). You can repeat this watering as many times during the day as needed for your plants. Once you get an idea of what your plants need, you can set the system up on a timer. Also, always remember not to water at least two hours before shutting off the lights and whenever it is dark. You can find much of this information in the brochure “Watering and pH”.