Reducing Algae in Your Hydroponic System

Introduction - Algae.  I can’t lie.  I kinda like the stuff.  Some say it produces as much as 70% of the oxygen in our atmosphere, it may help us solve global warming, it creates amazing light shows in the ocean, and it can even be pretty darn healthy.  But, let’s face it…none of us want significant amounts of algae in our hydroponic systems. 

It’s important to realize that there will almost always be some algae in your hydroponic system.  Where there are nutrients, water and light, there will always be algae at some point.  It is, whether we like it or not, part of a healthy ecosystem.  But, it can also get out of control, and steal nutrients from our hydroponic garden, while also impacting you pH levels.  So, to keep it under control, here are a few helpful tips for reducing algae in your hydroponic system.

Tip #1 – Always use clean supplies when filling your hydroponic reservoir.  Occasionally, I’ll hear from somebody who just bought a new iHarvest® indoor garden and is experiencing a huge outbreak of algae in their system.  The first thing I ask, is what container they used to fill their system with.  Most of the time, I hear about the old bucket laying around in the garage or basement.  These old buckets and hoses will often carry trace amounts of algae spores that you can’t detect, so please do yourself a favor by disinfecting them, or purchasing something new to fill your hydroponic reservoir with.

Tip #2 - Add 10ml of 3% Hydrogen Peroxide (H202) for every gallon of water in your hydroponic system.  You can do this as often as 3x a week, or you can do this only when you sense a problem.  It does a great job of eliminating algae overgrowth, and it happens to be a great solution for fungus gnats as well.  Food grade H2O2 is nice, but can be harder to find.  It often comes in much stronger solutions than the 3% you need for your hydroponic garden.  Finding 35% food grade H2O2 is common, so simply make sure to add 11.5 ml of water to every 1 ml of 35% food grade H2O2 you may get your hands on.

Tip #3 – Try Using Hydroguard as an additive to your hydroponic system.  I hesitate to suggest a specific brand, but this is the one my customers go to again and again.  Hydroguard actually contains an isolated strain of bacteria known as bacillus subtilis.  These bacteria may help to improve your yields by preventing root rot and increasing nutrient availability.  But they also seem to compete with algae, which keeps it at bay.  Just remember not to add hydrogen peroxide within 48 hours of adding the Hydroguard, as the hydrogen peroxide will kill the beneficial bacteria as well.

Tip# 4 – Block light from getting inside your hydroponic system.  Some light will always enter your hydroponic system, but algae needs light to survive.  So, make sure you don’t let any unnecessary light inside your hydroponic system.  Keep all of the lids to your reservoir closed, and limit allowing light into other areas to the extent reasonable.  For instance, some people purchase reflective, hydroponic net pot covers to keep light from getting into their system from around the plant roots.  This is a nice solution for keeping algae at bay over the long term.

Tip #5 – Add 5-10 drops of grapefruit seed extract per gallon of water in your hydroponic system.  I haven’t actually used this to control algae in my systems, and I haven’t heard many success stories, so this solution is further down the list.  But, if you’re interested in experimenting, this may be the solution for you.

Tip #6 – Add a UVC light to your system.  Ultraviolet light will kill algae and other microorganisms.  However, UV light can be damaging to plastics that do not use UV additives.  The iHarvest does not currently use UV protection additives in it’s plastic, so UVC lights are not recommended.