By Arielle Friedman

Ebb and flow, also known as flood and drain, is an effective hydroponics system that’s becoming increasingly popular for growing cannabis. It’s low in cost and intermediate in difficulty. If you’ve tried out some basic hydroponics systems and are ready to take things to the next level, ebb and flow might be for you.


In ebb and flow, plants are potted in an inert growth medium which provides no nutrition, but anchors the roots and drains slowly. The pots are then placed within a growing tray, which sits above a reservoir of nutrient-rich water. This water is pumped from the reservoir into the growing tray where it flows through holes in the pots to the roots of the plants. The water is then allowed to slowly drain back to the reservoir through the force of gravity. The roots then remain dry for a period and become oxygenated.

This is a kind of “fast and feast” model. During the flooding phase, the plant becomes “starved” for oxygen—so it feasts on O₂ when the roots are dry. Vice versa during the draining phase—the plants becomes thirsty and guzzle water.


Once set up, the ebb and flow system pretty much takes care of itself. It’s easy to maintain and works in a mostly automated way. They are also cheap and fairly easy to set up. It’s pretty simple—the limited exposure of the plant roots to the nutrient solution prevents the necessity of temperature control, water oxygenation, and other complicated factors common to other hydroponic systems.

Ebb and flow systems are known for their modesty—they’re quiet, take up little space, and don’t require much energy. If you need your hydroponics system to be unobtrusive, ebb and flow is a good choice.

Ebb and Flow


The major disadvantage of an ebb and flow system is that if something goes wrong, you could ruin your whole crop. This system needs monitoring, especially with new, untested equipment. If there is a problem, you’ll need a human brain to solve it!

Another disadvantage is that this growing method can lead to root diseases and nutrient insufficiency if you neglect sanitation and maintenance. Be sure to replace your nutrient solution weekly, and to clean all parts of the system between grows.

Poor drainage can tank this system, leading to root rot and other issues. Make sure to set everything up correctly from the start, and you should be good to go.



  • Reservoir with lid
  • Growing tray to sit above the reservoir
  • Rubber piping
  • Water pump with timer (a garden pond pump works)
  • Plants potted in an inert grow medium (such as coarse sand, clean gravel, or Rockwool cubes)

Ebb & Flow Cannabis


  1. Drill two holes in the lid of the reservoir; drill another two in the base of the growing tray, lined up to be directly above those of the reservoir.
  2. Connect two of the holes with an overflow tube, which sits above the expected water level in the growth tray and will catch excess water if flood levels run too high.
  3. Connect the other two holes with black tubing; this tube will act as both flood pump and drain. Attach the head of the pump in the reservoir to the mouth of this tubing.
  4. Place the potted plants in the growing tray. The pots should be about twice as tall as the edge of the growing tray.
  5. Set the timer on the pump. You should plan for the flooding period to last for 15 minutes, and the draining period to last for another 15.

How often to flood and drain? This depends on your grow medium and climate. In cooler climates, or with a slower-draining media like Rockwool, two floods a day should do the trick. In warmer climates, or with fast-draining media, you may go up to four floods a day, or even six.

There you have it—if you’re looking for an achievable challenge in the world of hydroponic growing, ebb and flow might be in your future!

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