Commercial growers invest heavily in their grow rooms, sourcing the best mother plants, nutrients, lights, CO2 generators and other expensive high-tech equipment, and meticulously setting it all up. Their expectation? A bumper crop and higher profits.
But reality often tells a different story. A single overlooked factor can compromise an entire operation. One of the main culprits? Poor hygiene—both plant and system. Neglecting cleanliness can lead to disease and reduced yields, compromising crop success.
Maintaining proper hygiene in a hydroponic system is essential for plant health and productivity. This blog post explores the most important aspects of hydroponic grow-room hygiene, from preventive measures and maintenance routines to effective cleaning strategies.
Importance of hygiene in hydroponic systems
Poor hygiene can be the culprit in a range of grow-room problems. Unhygienic conditions can promote yield-robbing diseases like powdery mildew or lead to failed microbial tests when it’s time to sell to dispensaries.[1] Hydroponic growers, especially those using recirculating systems, must be diligent because contaminants like bacteria can quickly spread throughout the system.[2]
Hygiene is more than just cleaning and sterilizing the grow room. Britannica defines it as “the science of preserving health.”[3] Healthy plants are more resistant to pathogens, so promoting plant health is a critical part of any hygiene strategy. This includes practices like sourcing healthy seeds or seedlings, fertigating essential nutrients in the right balance and maintaining optimal environmental conditions, from the grow room to storage.
Common contaminants that affect cannabis
Contaminants can be introduced at many stages: cultivation, harvesting, drying, curing or extraction. Below are some of the most common types found in cannabis grows, along with steps for preventing or eliminating them.
Biofilm and algae
Although often confused due to their similar appearance in water, biofilms and algae are distinct. Biofilms are slimy bacterial colonies that form on surfaces in hydroponic systems. Algae are photosynthetic, plant-like organisms.[4] Both can deplete dissolved oxygen, clog systems, attract pests and reduce water and nutrient uptake.
Biofilm and algae
Although often confused due to their similar appearance in water, biofilms and algae are distinct.
Plant debris and organic matter
Plant debris and other organic matter can clog irrigation systems and contribute to the formation of biofilm and algae.
Post-harvest microbial contamination
Because cannabis has a high moisture content at harvest,[5] it’s highly susceptible to mold when humidity is high or air circulation is poor. Other post-harvest microbial contaminants include powdery mildew, botrytis, budworm and mites. Improper harvesting, drying and storage—particularly under damp conditions—is a leading cause of microbial contamination.[6]
Pests and pathogens
Densely planted grow rooms are vulnerable to rapidly spreading pests or pathogens. Fungi, bacteria and viruses can cause diseases like root rot, powdery mildew and hop latent viroid, reducing yield and quality. Viruses are often introduced through contaminated tools, infected plant matter or even human contact, making strict hygiene protocols, including regular hand washing, essential for prevention.[7]
Pests like aphids, leaf miners and loopers can also infest grow rooms, damaging plants by chewing, sucking or burrowing through tissue. These insects may enter via new plant material, ventilation systems or small structural gaps.[8]
Pests and pathogens
Densely planted grow rooms are vulnerable to rapidly spreading pests or pathogens. Fungi, bacteria and viruses can cause diseases like root rot, powdery mildew and hop latent viroid, reducing yield and quality. Viruses are often introduced through contaminated tools, infected plant matter or even human contact, making strict hygiene protocols, including regular hand washing, essential for prevention.[7]
Pests like aphids, leaf miners and loopers can also infest grow rooms, damaging plants by chewing, sucking or burrowing through tissue. These insects may enter via new plant material, ventilation systems or small structural gaps.[8]
Heavy metals
While more common in plants grown in soil,[9] heavy metals can also be introduced through poor-quality water or low-grade fertilizers made from contaminated raw materials. Cannabis is in a class of plants called hyperaccumulators that can accumulate metals in their tissues “at levels hundreds or thousands of times greater than is normal for most plants,” posing a potential health risk for consumers.[10]
Best practices for maintaining hygiene
While controlled environments like grow rooms and greenhouses help prevent the introduction of contaminants, the risk is never zero. Growers can take several measures to stop biotic and abiotic contaminants from proliferating indoors.
Train personnel and create protocols
A hygienic grow room should have clear SOPs that minimize the risk of contamination and ensure proper cleaning. Provide hygiene training for anyone who interacts with the plants or hydroponic system, and post signage in employees’ native languages as reminders. Have a plan for preventing contamination from sick or injured employees, such as requiring use of personal protective equipment, and ensure any reusable equipment is regularly sanitized and properly maintained.[11]
Train personnel and create protocols
A hygienic grow room should have clear SOPs that minimize the risk of contamination and ensure proper cleaning.
Provide hygiene training for anyone who interacts with the plants or hydroponic system, and post signage in employees’ native languages as reminders. Have a plan for preventing contamination from sick or injured employees, such as requiring use of personal protective equipment, and ensure any reusable equipment is regularly sanitized and properly maintained.[11]
Inspect and monitor plants and equipment
Plants are often the first sign of poor hygiene, so frequent, regimented inspections are a necessity:
- If your system allows root visibility, examine the roots; they should be white and firm. Brown, soft roots usually indicate root rot.[12]
- Next, check the foliage. Signs of potential issues include:
- Curled, yellowing, browning or wilting leaves
- Spots or irregular leaf patterns
- Necrosis (i.e., tissue death)
- Yellowing between leaf veins
- Holes in leaves
- Visible pests
- Discoloration
- If your system allows root visibility, examine the roots; they should be white and firm. Brown, soft roots usually indicate root rot.[12]
- Next, check the foliage. Signs of potential issues include:
- Curled, yellowing, browning or wilting leaves
- Spots or irregular leaf patterns
- Necrosis (i.e., tissue death)
- Yellowing between leaf veins
- Holes in leaves
- Visible pests
- Discoloration
These symptoms may point to nutrient deficiencies, pests, disease or environmental stress.
Also inspect equipment for issues like biofilm buildup. Monitor for plant debris and organic matter, and remove them from the system when possible.
Implement IPM
Integrated Pest Management (IPM) is a comprehensive approach to pest and disease control that minimizes pesticide use. See our blog post Managing Cannabis Pests and Pathogens for tips on implementing IPM in your grow room.
Use a high quality water source
A hygienic hydroponic system depends on a clean, healthy water supply. Water should be free of bacteria, heavy metals and water-soluble salts, all of which can contaminate your system.
Test water before use and filter and sterilize it as needed. Purification options include:
- UV irradiation
- Chemical disinfectants (e.g., chlorine, hydrogen peroxide, ozone)
- Biological controls
- Plasma-based treatments
- Reverse osmosis
Test water before use and filter and sterilize it as needed. Purification options include:
- UV irradiation
- Chemical disinfectants (e.g., chlorine, hydrogen peroxide, ozone)
- Biological controls
- Plasma-based treatments
- Reverse osmosis
Maintain optimal environmental conditions
Diseases and mold often thrive in damp environments. Maintain proper airflow and ventilation, along with temperature and humidity levels tailored to each growth stage. Refer to a VPD chart to stay in the optimal zone. HEPA filters in HVAC systems can help reduce airborne fungal spores.[17]
To avoid post-harvest microbial contamination, maintain humidity at 50‒55% and temperature at 18‒21°C during hang or screen drying, with light air circulation. For medicinal cannabis, store trimmed buds at 18°C and 45‒55% humidity.[18]
Manage the nutrient solution
Essential nutrients are vital to plant health and resilience. Choose high-quality fertilizers formulated for cannabis to avoid heavy metal contamination and to deliver the proper nutrient balance.
However, nutrients, which are delivered as soluble salts, can themselves become contaminants via salt accumulation, especially in recirculating systems. Regularly test nutrient solution levels and measure runoff to check for salt buildup. Runoff can also be tested for pathogens and biofilm.
Manage the nutrient solution
Essential nutrients are vital to plant health and resilience. Choose high-quality fertilizers formulated for cannabis to avoid heavy metal contamination and to deliver the proper nutrient balance.
However, nutrients, which are delivered as soluble salts, can themselves become contaminants via salt accumulation, especially in recirculating systems. Regularly test nutrient solution levels and measure runoff to check for salt buildup. Runoff can also be tested for pathogens and biofilm.
Sanitize and sterilize equipment
All system components should be sanitized and sterilized between uses—including trays, tools, reservoirs and pipes. Spray down reservoirs, trays and pumps to remove plant debris or algae.[19] Clean any surfaces that come into contact with nutrient solution or plant material with detergent and water to remove organic matter. Then sterilize with a disinfectant that’s safe for your setup. Options include:
- Eco-friendly: vinegar, hydrogen peroxide or citric acid
- Stronger chemicals: chlorine dioxide or peracetic acid[20]
Remember to let all surfaces dry completely before reuse.
Eliminate biofilm
Biofilm is difficult to eliminate once established. Chlorine or hydrogen peroxide can work, but they may harm beneficial root microbes and require downtime. Worse, if not completely removed, biofilm can regenerate and become more resistant.[21]
Instead, use an enzyme-based cleaner like Emerald Harvest’s Hydra Clear, which breaks down biofilm at the molecular level without harming plants or equipment. Aqueous ozone is another option; see our white paper Stratospheric Yields: Optimal Use of Aqueous Ozone in Hydroponic Systems for more on this treatment.
Eliminate biofilm
Biofilm is difficult to eliminate once established. Chlorine or hydrogen peroxide can work, but they may harm beneficial root microbes and require downtime. Worse, if not completely removed, biofilm can regenerate and become more resistant.[21]
Instead, use an enzyme-based cleaner like Emerald Harvest’s Hydra Clear, which breaks down biofilm at the molecular level without harming plants or equipment. Aqueous ozone is another option; see our white paper Stratospheric Yields: Optimal Use of Aqueous Ozone in Hydroponic Systems for more on this treatment.
Instead, use an enzyme-based cleaner like Emerald Harvest’s Hydra Clear, which breaks down biofilm at the molecular level without harming plants or equipment. Aqueous ozone is another option; see our white paper Stratospheric Yields: Optimal Use of Aqueous Ozone in Hydroponic Systems for more on this treatment.
Conclusion
Despite growers’ best efforts, it’s nearly impossible to keep contaminants completely out of the grow room and hydroponic system. But by educating personnel, taking preventive measures and addressing contaminants as soon as they’re detected, cannabis growers can maintain a hygienic system that supports healthy plant growth and results in high-quality buds.
Emerald Harvest Team
[1] Schiller, Melissa. 2020. “Most of Colorado’s Failed Cannabis Tests Stem from Microbials: Here’s What Cultivators and Dispensaries Can Do About It.” Cannabis Business Times, May 13. https://www.cannabisbusinesstimes.com/interviews-opinion/news/15691671/most-of-colorados-failed-cannabis-tests-stem-from-microbials-heres-what-cultivators-and-dispensaries-can-do-about-it.
[2] The Northeast Center to Advance Food Safety. n.d. “Personal Health and Hygiene.” Accessed August 5, 2025. https://www.uvm.edu/d10-files/documents/2024-06/Personal_Health_Hygiene_Produce_Safety_Hydroponic_Aquaponic_Operations.pdf.
[3] Brittanica. “Hygiene.” September 13, 2017. Accessed August 5, 2025. https://www.britannica.com/science/hygiene.
[4] Dunn, Bruce, and Teal Hendrickson. 2021. “Algae Control for Greenhouse Production.” OSU Extension, September. https://extension.okstate.edu/fact-sheets/algae-control-for-greenhouse-production.html.
[5] Callahan, Chris. 2021. “Drying and Curing Herbs and Flowers (Hops, Hemp, and Everything Else!).” UVM Extension Ag Engineering, February 23. https://blog.uvm.edu/cwcallah/2021/02/23/drying-and-curing-herbs-and-flowers-hops-hemp-and-everything-else/.
[6] Dryburgh, Laura M., Nanthi S. Bolan, Christopher P.L. Grof, et. al. 2018. “Cannabis Contaminants: Sources, Distribution, Human Toxicity and Pharmacological Effects.” British Journal of Clinical Pharmacology 84 (11): 2468–2476. https://doi.org/10.1111/bcp.13695.
[7] The Northeast Center to Advance Food Safety. n.d. “Personal Health and Hygiene.” Accessed August 5, 2025. https://www.uvm.edu/d10-files/documents/2024-06/Personal_Health_Hygiene_Produce_Safety_Hydroponic_Aquaponic_Operations.pdf.
[8] Bessin, Ric, Lee H. Townsend, and Robert G. Anderson. n.d. “Greenhouse Insect Management.” University of Kentucky College of Agriculture, revised April 2007. https://entomology.ca.uky.edu/ent60.
[9] Mulyukin, Maksim A., Oleg S. Sutormin, Zoya A. Samoylenko, et. al. 2024. “Heavy Metal Content in Medicinal Plants Grown in Hydroponics and Forest Soil in the Central Part of Western Siberia.” Forests 15 (9): 1606. https://doi.org/10.3390/f15091606.
[10] Seltenrich, Nate. 2023. “Untested, Unsafe? Cannabis Users Show Higher Lead and Cadmium Levels.” Environmental Health Perspectives 131 (9): 094001. https://doi.org/10.1289/EHP13519.
[11] The Northeast Center to Advance Food Safety. n.d. “Personal Health and Hygiene.” Accessed August 5, 2025. https://www.uvm.edu/d10-files/documents/2024-06/Personal_Health_Hygiene_Produce_Safety_Hydroponic_Aquaponic_Operations.pdf.
[12] Liang, Jiayu. 2024. “Diagnosing Houseplants 101: Is Your Plant Diseased or Just Overwatered?” University of Florida Emerging Pathogens Institute, July 3. https://epi.ufl.edu/2024/07/03/diagnosing-houseplants-101-is-your-plant-diseased-or-just-overwatered/.
[13] Techniques in molecular biology used to amplify and detect DNA or RNA sequences from small samples. These methods are crucial for identifying plant pathogens such as viruses and viroids.
[14] Buirs, Liam, and Zamir K. Punja. 2024. “Integrated Management of Pathogens and Microbes in Cannabis sativa L. (Cannabis) Under Greenhouse Conditions.” Plants 13 (6): 786. https://doi.org/10.3390/plants13060786.
[15] Alhoshy, Mohamed A., Farag A. Samhan, Ahmed S. El-Gendy, and Taha M.A. Razek. 2025. “Characteristics and Attempts for Treatment.” Water, Air and Soil Pollution 236: 463. https://doi.org/10.1007/s11270-025-08077-w.
[16] Morard, Phillippe, Ludovic Lacoste, and Jerome Silvestre. 2008. “Effect of Oxygen Deficiency on Uptake of Water and Mineral Nutrients by Tomato Plants in Soilless Culture.” Journal of Plant Nutrition 23 (8): 1063–1078. https://doi.org/10.1080/01904160009382082.
[17] Buirs, Liam, and Zamir K. Punja. 2024. “Integrated Management of Pathogens and Microbes in Cannabis sativa L. (Cannabis) Under Greenhouse Conditions.” Plants 13 (6): 786. https://doi.org/10.3390/plants13060786.
[18] Ubeed, Hebah Muhsien Sabiah A.L., Ronald B. H. Wills, and Jayani Chandrapala. 2022. “Post-Harvest Operations to Generate High-Quality Medicinal Cannabis Products: A Systematic Review.” Molecules 27 (5): 1719. https://doi.org/10.3390/molecules27051719.
[19] Hoidal, Natalie, Amanda Reardon, Leah Worth and Mary Rogers. 2022. “Small-Scale Hydroponics.” University of Minnesota Extension, accessed August 5, 2025. https://extension.umn.edu/how/small-scale-hydroponics.
[20] Requires careful handling.
[21] Zylstra, Al. 2014. “You’ve Got Biofilm.” GrowerTalks, March 26. https://www.growertalks.com/Article/?articleID=20666.
