The Other Route: Keeping the Reservoir Sterile
Some would argue that one of the strengths of hydroponics is its sterile environment, and the notion of exposing growing systems to bacterial and fungal organisms would be self-defeating, if not sacrilegious. These growers rely on sterile growing environments, strong disinfectants and a product like SM-90. Another option is Hydrogen Peroxide. Each of these offer their own protection and benefits. But NEITHER SM-90 or Hydrogen Peroxide works well with organic aditives in the reservoir. They do not work well together and SM-90 has also been known to react poorly with Superthrive.
In a sterile growing environment, your goal is to have a super clean reservoir. This is harder than it sounds. Folks who have been growing in the same area with the same equipment for years might find that they are suddenly having root problems when they never had them before. Or a new grower might begin having problems right from the beginning.
Keeping your reservoir totally sterile can work very well, but once you get a population of icky badness it will keep coming back again and again. Some pathogens such as pythium are almost impossible to get rid of completelely. No matter how many times you sterilize everything with a bleach solution, the problem returns. It can get very frustrating and expensive to constanly be battling. More and more innovative growers are moving toward a more wholistic approach of using good microbes in the reservoir.
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Root Rot and Pythium
"Root rot" is a generic name for several common opportunistic waterborne diseases that can seriously affect indoor and outdoor crops year round. "Pythium" is the name of one of these diseases and is also used as a generic term for several different root rot and stem rot fungus species (including Pythium, Verticillium, and Phytophthora, and Fusarium). The term “damping-off” is also often used and usually applies to disease in seeds, seedlings and clones.
Whatever you call them, these diseases attack the roots of a plant and can rapidly infect crops in all stages. Damage includes reduced yields and crop failure. Pythium is particularly damaging in recirculating hydroponic systems as they provide ideal conditions for rapid growth and spread of infectious spores; a single infected plant can breed and send spores to all the plants.
The best thing is to prevent root rot from ever taking hold in the first place. It is an opportunistic disease which means that it is looking for sick, injured or weakened plants. Pythium is almost impossible to 100% eradicate from an infected system; this involves starting completely over (with new parents, containers, equipment, etc). It is probably present even if you don't know it - just waiting for its chance to get in.
“The best preventative measure against Pythium attack is a healthy, rapidly growing plant as this is an opportunist pathogen and will enter at the site of tissue injury or if the plants are overly succulent, weakened or stressed for some reason. Often root damage during the seedling stage as plants are introduced to the hydroponic system is a danger time for Pythium infection. Pythium is of greatest threat during the seed germination and seedling development stage when plants are most vulnerable to attack, and adequate control and elimination of the pathogen during this stage is the best preventative measure of Pythium control in hydroponic systems. Strong healthy plants will develop resistance to Pythium attack during the seedling stage and this will prevent problems at a later stage of growth. “
Dr. Lynette Morgan, Growing Edge Magazine
"Nutrient Temperature, Oxygen and Pythium in Hydroponics"t
http://www.hydromall.com/grower/pythium_in_hydroponics.html
How to Avoid a bad case of Root Rot
Monitor plants and roots frequently
Maintain a clean system – change and sterilize reservoir weekly.
Design your system to combat pathogens
keep your nutrient reservoir between 68 and 72F to maximize root growth, Dissolved Oxygen levels and inhibition of Pythium. 80 degrees and above will bring on a fast case of root rot.
Constant aeration – maintaining high dissolved oxygen levels inhibits pathogens and accelerates root growth
keep a lid on your reservoir to keep plant matter and light out
Maintain a low pH of 6.2 or less to inhibit pythium growth
Use prevention!! Use tank additives to give your roots the edge they need to grow strong and healthy!! Check out the Roots and Prevention section.
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Bacterial slime and other horrifying nasties
These are not the beneficial bacteria and fungi that we have already spoken about. These bacteria cause cloudy reservoirs, slimy build up, weird reservoir fuzz, gelatin growths and wild pH fluctuations. These are the reservoir monsters.
When these bad microbes are present at high populations and are happily feeding on organic matter, they use up just about all the oxygen in the nutrient solution, suffocating the plants. They release toxic substances as a biproduct of their life cycle. They also suppress the good microbes at the root zone and cause problems with nutrient uptake and plant growth.
Bacteria slime and cloudy reservoirs
Bacteria can make the water cloudy, but tend to produce more of a slime or jellylike, smelly mass in the system.If you have it, you will notice slimy reservoir walls and perhaps an oily slick on the water. Another symptom can be a foamy buildup in the reservoir. If left to their own devices, these bacterial growths will smother the roots, depriving them of oxygen. Some species of anaerobic bacteria thrive in an environment deprived of oxygen and can produce chemical metabolites, such as alcohols, aldehydes, phenols and ethylene, that are toxic to plant roots and to other microorganisms.
Other symptoms of bacterial infections can be fuzzy, cotton like growths, or the growth of fur. Just in case you are wondering, that white fuzzy growth you see at the tip of your roots is desireable. That is not bacteria - That is the good stuff - you should see tiny fine white hairs at thje roots.
All of these nasties require organic matter to feed on. They may be there as the result of a buildup of dead roots and leaves in the root zone, but usually they are the result of adding an organic product to the reservoir. If the conditions are just right, the bacteria will begin to thrive.
One option is to use no organic additives at all and to rely strictly on chemical nutrients based on fertilizer salts. We think a better choice is to continue using organic material, but also using an enzymatic addtive like Hygrozyme that will break down the unwanted organic matter in the reservoir . If you would like to use additives such as bat guano, compost or fish-based products, you might consider run to waste instead of a recirculating system.