Step By Step: Batch Culturing Algae
By Joshua Matthews
At EcoTrophic Solutions, we’re thrilled to unveil our very first piece of educational content: a step-by-step video guide on mastering the art of algae cultivation. From properly sterilizing your equipment to setting up and connecting everything seamlessly, this comprehensive tutorial leaves no stone unturned. We’ve also included a detailed breakdown of all the materials you’ll need to get started. But that’s not all—keep scrolling to explore more tips in our blog post, featuring printable protocols and stunning graphics to help make your algae-culturing journey a success.
What you will need
To start your cultures
Algae Starter Culture (We have been using Raphidocelis subcapitatat)
A heating source for initial sterilization (stove top or burner)
A pot for boiling water (should be able to fit your culture vessels)
Alternatively, an autoclave reduces the need for the heat source and pot for boiling
Grow lights (ours are on a timer with 16 hours light, 8 hours dark)
Air pump, aquarium airline (3/16 in), airline gang manifold
Filtered water (tap water contains chlorine and other materials that are harmful to algae)
To maintain your cultures
A bottle brush
scrub pad
3% to 5% hydrogen peroxide
transfer pipette
Measuring cup (250ml or 1 cup)
Nutrient Solution (We have been using Guillard’s F/2)
Once you’ve gathered all the necessary materials, you’ll also need a culture vessel equipped with a mechanism to deliver air deep into the vessel. This ensures the algae remains aerated and well mixed. We recommend using glass vessels with metal and rubber components, as they are durable and can withstand frequent use and the intense conditions of heat sterilization. These vessels are conveniently available in our online store, right here on our website.
Algae culture vessel diagram. Note that using gel nail polish is the best way to label and track your culture vessels as it can withstand rigorous cleaning and the intensity of grow lights.
Sterilization
Sterilization is a critical step in algae cultivation, as it prevents contamination and ensures the purity of your cultures. Contaminants such as bacteria, fungi, or other microorganisms can outcompete algae for nutrients, disrupt growth, and compromise the quality of your research or production. By starting with clean, sterilized equipment, you set the foundation for a successful and uncontaminated growing process.
We specifically use glass and metal materials for our culture vessels because they can withstand rigorous heat sterilization without degrading or leaching harmful substances, which is a common issue with plastics. All new equipment is carefully sterilized using high-temperature methods, such as boiling for 15-30 minutes, to eliminate any microorganisms that may be present on the surfaces. Following boiling, every material that comes into contact with the culture solution is meticulously scrubbed with 3-5% hydrogen peroxide. Hydrogen peroxide is the cleaner of choice because it effectively eliminates contaminants while breaking down into harmless hydrogen gas and water, avoiding the risk of residual chemicals that could interfere with algae growth. In contrast, cleaners like bleach can leave behind chlorides and other compounds, posing long-term contamination risks.
Maintaining a strong commitment to sterilization is essential for achieving optimal algae growth while minimizing variables that could compromise results or reduce production efficiency. Heat sterilization is primarily required when using growth equipment for the first time or when addressing contamination issues that may lead to culture crashes. However, between each batch of algae, it is crucial to scrub the culture vessels with hydrogen peroxide. This ensures the removal of residual contaminants and prevents the introduction of unwanted microorganisms, safeguarding the integrity of future cultures.
Nutrients and Inoculation
After constructing and thoroughly sterilizing your culture vessels, the next step is to prepare them with the growth medium and inoculate with a healthy algae culture. In the Aquatic Biodiversity and Conservation (ABC) lab at the University of Nebraska–Lincoln, we use 4 ml (~0.8 teaspoon) of Guillard’s F/2 solution per gallon of culture water, measured with a transfer pipette. This nutrient solution has proven effective for many algae species, but it’s important to note that other species may have specific requirements. For example, marine algae often require added salts, and diatoms may need silicates. Always consult the manufacturer’s guidelines to ensure the proper dosage for the specific nutrient solution you are using and read relevant literature about the specific needs of the algae you plan to culture.
For inoculation, we recommend adding 250 ml (one cup) of a healthy algae culture per gallon of new culture water. While smaller volumes, such as 50 ml per gallon, can be used, we’ve found that this increases the risk of other microorganisms outcompeting the algae we aim to cultivate. Using a larger inoculation volume not only promotes healthier cultures but also accelerates the time required for the culture to mature before harvest. However, it’s important to strike a balance—adding excess nutrients provides no added benefits and may even result in a culture crash.
There are many reputable suppliers of algae starter cultures online, making it easy to source high-quality inoculate. Once you’ve established a healthy algae culture, you can reserve a portion of it for re-inoculation while harvesting the remainder. With our setup at the ABC lab, using the species Raphidocelis subcapitata, we typically harvest our culture vessels weekly. Although the cultures could be harvested every five days, we find it easier to manage the schedule on a weekly basis. Depending on factors such as the algae species used and the amount of light available, you can expect to harvest algae every 3 to 10 days
Harvesting the Algae
Harvesting algae is a straightforward process and an essential component of multi-species and multi-trophic aquacultural practices, promoting sustainability and efficient nutrient cycling. In our setup, we first set aside a portion of the culture for re-inoculation before pouring the remaining contents of the culture vessels directly into the tanks being fed. Cultured algae serves as an excellent, nutrient-rich food source for zooplankton, such as Daphnia, and minnow fry. Through experience, we’ve found that feeding live algae dramatically improves the success of rearing Daphnia and minnows compared to using powdered algae or other processed foods, enhancing growth rates and overall health.
In multi-trophic aquacultural systems, where various species interact and depend on each other for nutrients and waste recycling, live algae plays a crucial role in maintaining ecosystem balance and supporting the growth of higher trophic levels. The nutrients within the culture vessels should not be a concern during harvesting, as they are generally depleted during the culturing process. However, if feeding more sensitive species where separating the algae from the culture medium is necessary, you can use a fine mesh filter (less than 35 micrometers) or other filtration methods to remove algae particles from the nutrient solution. This extra step ensures the health of sensitive organisms while maintaining the integrity of the aquaculture system.
After harvesting the algae, it’s time to prepare the culture vessel for the next batch. Start by thoroughly scrubbing the vessel with a small amount of hydrogen peroxide to eliminate any residual contaminants. This step ensures that your culture remains clean and free from unwanted microorganisms. Once sterilized, rinse the vessel, fill it with clean water, and carefully add the appropriate amount of nutrients. Then, reintroduce the inoculate you set aside earlier to kickstart the next cycle of growth. Finally, reconnect the vessel to the air supply to maintain aeration and place it under your grow light to provide the conditions necessary for optimal algae cultivation. With consistent care, proper sterilization, and attention to detail, an algae culture can be sustained indefinitely, offering a renewable resource for your multi-species or multi-trophic aquacultural system.
Algae growing protocol used by the University of Nebraska Lincoln Aquatic Biodiversity and Conservation lab
A printable PDF version of this protocol is available to download here.
Have questions or need more tips on culturing algae? Don’t hesitate to reach out to us at EcoTrophicSolutions@gmail.com or simply use the form below—we’d love to hear from you! Thank you for reading, and happy growing! Here’s to thriving cultures and successful harvests!
healthy Raphidocelis subcapitata algae cultures at the University of Nebraska - Lincoln’s Aquatic Biodiversity and Conservation Lab. The left most cultures are 2 days old, the middle 2 rows of cultures had just been inoculated, and the right most rows are 5 days old.