Hydrogen Peroxide VS Bleach in Hydroponics: Which is Better?

Should you use bleach or hydrogen peroxide as disinfectant for your hydroponic gardening? I neglected this aspect the first time I jumped into hydroponics and I faced highly diseased peppers and basil! After experiencing that, I compared which is a better sanitation agent—hydrogen peroxide or bleach? Here’s what I got.

Hydrogen peroxide is the safer option to mix in nutrient water as treatment for disease prevention in hydroponic systems, as it does not produce harmful by-products. Conversely, bleach is more applicable for disinfecting the hydroponic system and garden tools at the end of growing seasons.

For us to decide which one to choose, we need to consider several factors such as 1) composition; 2) mode of action and effectiveness; 3) health and environmental safety; and 4) cost and accessibility. Continuing to read below might answer your long-held questions, so let’s now dive in!

When to Use Hydrogen Peroxide in Hydroponic?

Diluted food-grade hydrogen peroxide can be mixed with the hydroponic nutrient solution to clean the water in the system. This will lessen possibilities of root rot, algae, and their spread.

One of the disadvantages of HP is its instability. When you use it to clean garden tools with dirt or organics, it might not be that effective. This means before using HP, you’ll need to clean the surface first with water and remove any soil or dirt.

Thus, I think that bleach would be better to do that job and it is wiser to use hydrogen peroxide in cleaning the nutrient water system itself.

When to Use Bleach in Hydroponic?

In hydroponic systems, bleach will be more applicable when cleaning the hydroponic system and garden tools at the end of every growing season.

To do this, bleach must be carefully diluted in cold water. It is important to remember that hot water should not be used because it will degrade the active ingredient in bleach. Thus, it will not be effective.

Using old bleach will not be effective as well. Remember that bleach decomposes along with time. Thus after long periods in storage, its efficacy is also compromised.

Some other factors that affect bleach effectiveness are pH and temperature. It will release a toxic gas once exposed to hot temperatures or acidic compounds.

Hydrogen Peroxide Vs Bleach

In terms of composition, safety in terms of chemical by-product, non-corrosivity, and environment-friendliness, hydrogen peroxide is better for hydroponics gardening.

Personally, I use hydrogen peroxide more often than bleach. I mix hydrogen peroxide in my nutrient water to prevent root diseases such as root rot. While I use bleach only when cleaning my hydroponic system reservoir and gardening materials.

For us to have an in-depth understanding why hydrogen peroxide is better in hydroponics, let us consider the following factors:

1- Composition

Hydrogen peroxide is clear in color and comes from dissolving in water a chemical called barium peroxide obtained from burning barium salt. Whereas bleach is yellow in color and composed of sodium hypochlorite.

Hydrogen and oxygen, the main components of hydrogen peroxide (H₂O₂), are naturally-occurring. This makes it odorless and clear. It is just like adding another molecule of oxygen in water (H₂O)!

Conversely, bleach is yellow in color. It is also referred to as liquid chlorine, but it is actually not chlorine! Remember, that chlorine is always a gas. We will know why chlorine is always associated with bleach later in this article.

2- Mode of Action and Effectiveness

Hydrogen peroxide attacks the cell walls of bacteria, fungi, yeasts, and spores. On the other hand, bleach attacks protein in microorganisms.

In terms of effectiveness, there is no doubt that both of them really disinfects and sanitizes. However, we should know when to use hydrogen peroxide and when to use bleach.

3- Health and Environmental Safety

Hydrogen peroxide is biodegradable and more environmentally-friendly. Whereas, bleach is still considered as a corrosive hazardous agent as it produces a dangerous by-product, chlorine gas.

Hydrogen peroxide (H2O2) breaks down into water (H2O) and oxygen (O). It does not give off harmful by-products as it decomposes fully.

Another advantage of hydrogen peroxide is it does not burn! Have you ever accidentally touched bleach? It slightly burns, right? This is the reason why hydrogen peroxide is chosen as a common wound cleaner.

From here, we could conclude that bleach, indeed, needs extra caution when handling.

4- Cost and Accessibility

Bleach is cheaper and easier to find than hydrogen peroxide.

A huge advantage for bleach is its cheaper price. Bleach prices range from $0.99 per gallon to $5. While buying in bulk will be 12.5% cheaper at $0.90 per gallon.

While hydrogen peroxide is sold from $0.99 for 32 ounces to $35 per gallon. Buying in bulk will reduce this price by 70% at $10 per gallon.

This price was also considered when I recommended when to use each disinfectant. Since hydrogen peroxide is more expensive, combining it to your nutrient water just in small amounts would be practical.

Whereas, using bleach in cleaning large hydroponic systems and garden tools would take advantage of its cheaper price.

Should You Sterilize Your Hydroponic Systems?

Sterilization is a wise practice for every hydroponic gardener, since it ensures that the system is not prone to plant diseases that can decrease harvest.

Cleaning your whole system after every growing cycle is a good practice. It will lessen chances of spread of plant pathogens across growing seasons.

This is important because as a food grower, your number one concern must always be the safety and cleanliness of your harvest—human health must be a priority.

Furthermore, if you are someone who is venturing to commercialization, sanitation is also a key factor in certifications and health standards. A clean hydroponic system will reflect the standards your business is establishing.

How to Use Disinfectants in Hydroponics?

Disinfectants can be used before, during and after growing hydroponic plants.

Before and after every growing season, you need to make sure that your hydroponic system is free of disease-causing debris of old plant parts or even growing medium.

Remember that harmful microorganisms can cling onto these, so you need to remove them. When doing this, I recommend using bleach.

While your plants are growing, you also need to ensure plant health! Thus, disinfectants such as hydrogen peroxide would be helpful to clean your hydroponic nutrient water.

By adding hydrogen peroxide in your nutrient solution, you decrease the chance of survival of root rot pathogens. These pathogens will further cause diseases that can lead to your plant’s death.

Hydrogen Peroxide

In order to dilute food-grade hydrogen peroxide, 2 to 3 teaspoons must be added for every gallon of water.

If you are using this for water treatment, just use the same measurement per gallon. For example, if your nutrient film technique has a 10 liter water reservoir, you can use 20 teaspoons of hydrogen peroxide.

In cleaning garden tools, first make sure that the materials are free of plants or grow medium debris. You can use the same amount. Afterwards, dip only the metal parts of your materials and wipe them afterwards using a clean towel. Dipping wooden or plastic parts can cause damage overtime.

Thus, if you have plastic or wooden tools, you can just spray them with the hydrogen peroxide solution and wipe them right after.

Bleach

To use bleach in hydroponics, mix 7 and half teaspoons per gallon of water.

For system cleaning, you may need additional materials such as brushes or scrubbers. First step is to make sure that the system or the tools are free of any organic debris. Use water to initially flush these materials.

Pour the diluted bleach and carefully scrub the system and/or garden tools. Rinse everything with running water. For garden tools, you could wipe it with a clean towel or cloth. For the hydroponic system, you can also use a clean towel or just let the system dry.

A Beginners Guide: Hydroponic Sanitation & Sterilization

Organic Hydroponic Disinfectant Alternatives

Vinegar, isopropyl alcohol, and thyme oil are among organic hydroponic disinfectants.

In a hydroponic system, vinegar and thyme oil can be used to disinfect the nutrient solution and prevent root rot. A study has proven that thyme essential oil is effective as a defense inducer of tomato against Fusarium wilt and gray mold in hydroponics.

On the other hand, isopropyl alcohol can be used as a sterilizing agent for garden tools and hydroponic systems.

Furthermore, these three alternatives also vary in terms of cost. Vinegar is way cheaper, followed by isopropyl alcohol; and thyme oil is the most expensive.

Now it is up to you if you’ll choose the traditional bleach, the environment-friendly hydrogen peroxide, or any of these organic alternatives!

Sources

• “Hydrogen peroxide and sodium hypochlorite disinfectants are more effective against Staphylococcus aureus and Pseudomonas aeruginosa biofilms than quaternary ammonium compounds” by Lineback, C.B. in Antimicrobial Resistance & Infection Control
• “Hydroponics: A Versatile System to Study Nutrient Allocation and Plant Responses to Nutrient Availability and Exposure to Toxic Elements” by Nguyen,N.T. et al. in Journal of Visualized Experiments
• “Sodium Hypochlorite to Hydrogen Peroxide: A Comparison” by COVID-19 CETA Technical Committee in Cleaning Equipment Trade Association
• “Scientists demonstrate a better, more eco-friendly method to produce hydrogen peroxide” by Benjamin, C. in University of Illinois Urbana-Champaign