Algae can sometimes be a major problem in hydroponic systems. Algae can be green, reddish-brown, or black.
It clings to conduits and channels, grows on media, and oozes from pumps and tubing, it basically clogs up the entire system.
Algae sometimes emit a foul odor as it decomposes in the nutrient solution. Heavy infestations can actually seal off media and substrate.
Effects of Algae in Your Hydroponic System
It depletes Nutrients intended for the crop and as it regenerates and decomposes it also depletes dissolved oxygen from the hydroponic system.
Depleting oxygen from the system creates the biological oxygen demand and subsequently causes roots to suffocate resulting in crop loss.
Algae on plant roots which eventually suffocates them make them more prone to attack by other opportunist pathogens.
Fungus Gnats are attracted to algae-like flies to dung – their larvae tunnel through the roots into stems and can wreak havoc with the health and vitality of hydroponic gardens.
Decomposing algae can also produce toxins detrimental to the plant’s health and well being – but beneficial to the continuation of algae and fungi.
The toxins produced by algae also serve as a food source for other harmful plant fungi, causing spikes in their population within the system.
Algae Control in Hydroponics
Channels, conduits, and gullies should have light-proof covers. Media beds can also be covered with a dark plastic film or even a layer of dry substrate. The substrate will act as a dry mulch. Algae will not grow on dry surfaces. You can never eliminate all light from the solution, but you can minimize it which in essence minimizes algae blooms.
An otherwise healthy hydroponic system can tolerate small amounts of algae. Once a system becomes overrun with algae the best option is to harvest your crops, clean up the entire system, and start over again.
Killing Algae in Hydroponic System
Commercial algicide products are of limited value, they do help to control blooms, however, when misused or overused they will also damage young or delicate root systems. In addition, once you add most algicidal products, the algae will regrow after the product is depleted within the system, requiring more of the algicide -a vicious cycle.
Hydrogen Peroxide for Hydroponic Algae Control
Hydrogen peroxide [H202] is water [H20] with an additional oxygen atom, when broken down into nutrient solution, it helps to add extra oxygen to your Hydroponic nutrient solution.
Grapefruit Seed Extract for Algae Control and Water Purification
One good organic control for algae in hydroponic systems is Grapefruit Seed Extract. It kills off algae, and there is no evidence that it harms the plants.
The use of grapefruit seed extract in estuaries, ponds, and municipal water supplies has been proven to work, and it is only recently being introduced into the hydroponics realm. GSE has beneficial anti-bacterial, anti-parasitical, and anti-fungal properties without any documented side effects. Its use has been labeled “Citricidal Water Purification” and has been proven effective in purifying water for many travelers.
At low concentrations, grapefruit seed extract is effective for hydroponic and aquaponic systems while offering very low toxicity to plants, in aquaponics, and fish tanks to fish.
Citricidal is concentrated grapefruit seed extract in a liquid form that kills most viruses, bacteria, yeast, and fungi.
In one test conducted in Chile by Dr. Carlos Roman, a Zoologist, grapefruit seed extract was tested as a remedy against the oxygen depleting algae in salmon tanks. The tanks remained free of algae, and there no were noticeable side effects. Doses between 75 – 200 ppm were used.
I have been using 5-10 drops per gallon of water – of course, this can vary with the concentration of the solution you are using -check the ppm.
See – TDS in Hydroponics