Front Row Ag Account Manager and Crop Advisor Mike Harnos and Technical Expert Tyler Simmons break down one of the hidden threats in controlled environment agriculture: algae in water systems. In this video, they cover:
- Why algae doesn’t always show up on water tests
- How algae blooms and biofilms clog emitters
- The impact of algae on pH stability and water absorption
- Best practices for tank cleaning and sanitization
- Proven strategies to keep irrigation systems free of algae over the long term
If you’re running a commercial facility, this discussion highlights critical steps to protect your fertigation system and prevent costly downtime.
Transcript:
Algae is tricky because it won’t show up on most water tests—people expect green scum, but algae has bloom cycles and often isn’t visible. It thrives when nitrogen and phosphorus are present; when it dies, the chlorophyll color fades and it looks gray, black, brown, or tan—a soft, smearable mass that you can almost roll between your fingers.
Algae prefers more alkaline environments, while hydroponic feeds typically run ~pH 5.8–6.0. That low pH makes the solution both a food and a slow death for algae, so you get continuous die-off in tanks and lines. Dead algae contributes to biofilm—these grow in layers, and when layers shear off pumps and pipes, they travel downstream and clog emitters.
You’ll often see a quarter-inch green “cap” of algae on rockwool blocks in the same rooms, which can change water absorption patterns and feed fungus gnats—basically a little mat that harbors disease vectors. If algae is growing in batch or holding tanks, its metabolism can drive localized pH swings, and pH drifting out of range is one of the worst problems you can have.
Facilities should have an SOP to drain and reset the main holding tank on a schedule—ideally soon after a fresh RO/pretreatment filter change (not the same day). Many tanks have literally never been drained or rinsed. Chlorine can help, but a heavy algae load can overwhelm a small residual. A common pattern is killing algae downstream at the injector, which creates a surge of dead biomass that then clogs mixers and drippers. The fix: drain and spray the tank clean, refill, and sanitize at the source, so the algae never flourishes in the tank to begin with.
If you sanitize the holding tank (e.g., with a small, consistent chlorine dose via a doser), you prevent the mass of dead material that would otherwise be created downstream. Treating only at the injection skid means you’re always killing something and sending it further into the system; treat the root cause and keep the tank clean so there’s nothing to kill later.
Not many facilities have UV/ozone loops on storage, and overdosing oxidizers can damage fertilizer; filtered water also loses natural protections (chlorine/chloramine), so adding back a little protection is logical. The history of water sanitation is basically this lesson—boil or sanitize the water, or people get sick. Any time water sits, it can harbor growth. Watch your water like a hawk: avoid peroxide-based cleaners that are harsh on fertilizers, start clean, and maintain a low, steady level of sanitation instead of waiting for a crisis and then shocking the system.
