Brewing a beneficial Microbe tea serves multiple purposes for growers in any medium. In DWC it promotes healthy roots and is the best way to counter the dreaded “DWC slime” which eventually leads to root rot. I would consider this tea essential for anyone looking to keep plants in DWC over a long period of time (e.g. mother plants). I also use it in my flowering room to increase yield, as well as my sub irrigated planter to promote root health. My tests have found that beneficial microbes allow you to run your DWC reservoir at 70-75F (vs the 66-70F that I recommended for sterile DWC)
Brewing a tea rejuvenates the microbes and allows you to multiply your colonies. This way you can use a fraction of the recommended dose and extend how long your products last. This is similar to using a ‘yeast starter‘ in homebrewing.
The master grower at Zevk Cultivation has experience running DWC at scale. He has told me that without a beneficial tea his mother plants will eventually get DWC slime, no matter how diligently the water temperatures and pH are monitored. Without beneficials, on a long enough timeline a nasty strain of bacteria will eventually outcompete everything else and lead to slime/root rot. This recipe produces a clean DWC friendly tea, unlike the plethora of unwanted bacteria you get in traditional compost tea.
Beneficial Microbe Tea Recipe:
- 2.5 Gallons (10L) de-chlorinated Water (Carbon Filtered or Campden tablets)
- Beneficial Bacteria (30mL Hydroguard OR 30 mL Miicrobial Mass OR 40mL Voodoo juice)
- 15g Mycorrhizal Inoculant (GreatWhite OR DynoMyco OR Mykos)
- 1 hand full of Earth Worm Castings
- 15mL Molasses
- Cheesecloth or Muslin Bag
- 1 Gallon Sprayer (optional for foliar feeding)
The beneficial microbe tea is brewed for 36-4 hours and is typically used at a rate of 1 cup per gallon (70mL/L). This recipe produces enough tea to inoculate 40 gallons of nutrient solution. After the initial dose a booster dose of 1 tbs per gallon (5mL/L) should be added after 5 and 10 days.
Beneficial Bacteria
Beneficial bacteria’s main benefit is to out outcompete other pathogens for resources in your reservoir. No matter how good your sterile practices, pathogens will eventually find their way into your reservoir. Keeping your reservoir at the appropriate temps slows down bacterial growth, but it is impossible to maintain a completely sterile environment. BUT if you have an established colony of beneficial bacteria then pathogens and cyanobacteria won’t stand a chance. You have a small army fighting your battles.
If you can find Miicrobial Mass I recommend it. In addition to the above mechanism for outcompeting pathogens, Miicrobial Mass increases the solubility of phosphorous which is essential for flowering plants. For inorganic phosphorus that is complexed to other minerals, the bacteria release the inorganic phosphorus from this complex by producing organic acids. These acids decrease the pH locally, which in turn solubilises the inorganic phosphorus and therefore it turns into a form that the plant can absorb.
Mycorrhizal Inoculant
A mycorrhiza is a mutual symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant’s rhizosphere, its root system. Mycorrhizae play important roles in plant nutrition, root health and water chemistry.
Mycorrhizal fungi form a mutualistic relationship with the roots of most plant species. In such a relationship, both the plants themselves and those parts of the roots that host the fungi, are said to be mycorrhizal. Relatively few of the mycorrhizal relationships between plant species and fungi have been examined to date, but 95% of the plant families investigated are predominantly mycorrhizal either in the sense that most of their species associate beneficially with mycorrhizae, or are absolutely dependent on mycorrhizae. The Orchidaceae are notorious as a family in which the absence of the correct mycorrhizae is fatal even to germinating seeds.
The mechanisms by which mycorrhizae increase absorption include some that are physical and some that are chemical. Physically, most mycorrhizal mycelia are much smaller in diameter than the smallest root or root hair, and thus can explore soil material that roots and root hairs cannot reach, and provide a larger surface area for absorption. Chemically, the cell membrane chemistry of fungi differs from that of plants. For example, they may secrete organic acids that dissolve or chelate many ions, or release them from minerals by ion exchange.
My experience with mycorrhizal inoculants in DWC has shown it causes healthy white roots that grow to a much larger size. I suspect that the fungi stimulate the roots and cause them to grow much larger than they otherwise would in a deep water culture environment.
Worm Castings
Worm castings are worm poop. Castings contain rich microbiological colonies that help fight root-borne plant diseases and repel insects. Worm castings are water-soluble allowing plants to quickly and easily absorb essential nutrients and trace minerals. Nutrients are readily available to plant material over a greater length of time and will not burn even the most delicate plants. Analysis of earthworm castings reveals that they are rich in iron, sulfur, calcium, nitrogen, phosphorus and potassium (NPK rating: 5.5.3)
Molasses
The purpose of the molasses is to feed the beneficial bacteria and fungi. Molasses has more nutrients than refined sugar, which should be avoided if possible. Get unsulphured molasses if available.
How to Brew the Tea
Brewing the tea is fairly simple. Put the worm castings in a cheesecloth, filter bag or hairnet and tie off the end. Mix all ingredients together in a bucket, starting with the water and molasses. Add 1-2 airstones and let it brew for 36-48 hours. It should start to foam up within a few minutes. Take note of the smell, it should be an earthy, mossy smell. If it ever starts to smell foul throw the tea away.
After 36-48 hours of brewing any unused portions should be refrigerated for up to 7-10 days.
Can you run a Perpetual Tea?
Unfortunately running a perpetual tea that you keep feeding molasses does not work out well. One bacteria within the solution typically takes over and dominates the others. Diversity is important for these teas and thus storing over 10 days is not advisable.
