The problem that you will run into is the fact that algae and marijuana prefer the same environmental conditions – where your marijuana plants will thrive, so will algae. They like water that is rich in nutrients and has light permeating through it.
For that reason, you should make sure your hydroponic equipment, including tubing, buckets, and reservoirs, is not completely clear but instead is made of an opaque material. Rock wool, a substrate used in hydroponic setups to support marijuana roots, is also a popular gathering place for algae.
Since algae need light to grow, you can take care of it through the control of the lights. This is not to say you should dim or turn off the lights – this would also have a negative effect on your light-loving plants!
Instead, make sure your equipment is dark opaque in color, and try covering your rock wool with a landscape fabric. This will give the rockwool some space without allowing light to permeate through.
Once you see algae growing in your hydroponic or aeroponic system, you should clean your entire system and remove anything that is made of a clear material – replace them with an opaque version of the same thing. If you don’t have the money or time to replace them, you can also just try simply covering the clear equipment with some sort of dark material. If the algae are in the water itself, you can try a few other methods for clearing things up.
First, simply rinse out and clean the reservoir. Mix hydrogen peroxide (H2O2) with water at a 1:10 ratio. If you add this to the reservoir in minimal amounts but fairly often, you will give the roots of your marijuana plants an oxygen burst, giving them the ability to fight off algae growth. Because hydrogen peroxide can harm the roots of your plants, you should only do this for plants that are older and more developed since they can better withstand some harm.
If you use UVC lights in your system of filtration, micro organisms will be caught before they even make it to the grow room. These are the same types of lights that are often utilized with hot tubs, aquariums, etc. It won’t harm your marijuana plants, just like it won’t harm humans or many aquatic creatures. It will, however, take care of any potential algae problems.
Another method you can try using is grapefruit seed extract, which is actually used by many cities when treating their drinking water, as well as a natural way of handling the algae problems in fish ponds and lakes.
A final method that might work for your hydroponic reservoir is a barley straw mat. It’s an organic way of controlling algae in places like lakes, ponds, and other bodies of water that have the potential of algae. It is not an exterminant, so it won’t kill the algae that are already there. Rather, it slows down algae growth while not having any negative effects on any of the “good” organisms living there (including your marijuana plants).