The Best Way To Cure Root Rot

How to cure root rot

In hydroponic systems, root rot is caused by over-watering the roots. It's a tricky predicament to find yourself in considering hydroponics is entirely focused on growing plants in water and dissolved nutrients in the absence of soil.

Problems arise when the root system doesn’t receive sufficient levels of oxygen, typically when using the Deep Water Culture system or The Kratky Method. Either the water isn’t aerated enough, there’s no direct exposure of the roots to the air or a combination of the two. Once root rot takes hold, the slime creates an impenetrable barrier and oxygen cannot reach the plant. Think of it like a bullet-proof jacket except, instead of saving the plant's life, it kills it. Without suitable oxygen absorption, the root cells die, further opening the door for opportunistic pathogenic bacteria and fungi. Once they’ve infiltrated the dying cells, the pathogens can smother the rest of the living root system, too. 

Before we go any further, people want to know the products they'll need without having to read tons of, admittedly well crafted and thorough article, so here they are. These links will take you to Amazon, we've even done that work for you. HydroguardGreat WhiteAncient Forest - these are the products which host all of the microorganisms we're going to use to brew our tea. It's going to be a concoction of a billion beasts all battling one another in the infamous black bucket colosseum. What's their prize? Oxygen supplied by two airstones, sugar in the form of molasses, and the pride of their ancestors. All of this inside two gallons of distilled water. Read on for the recipe. 

Signs of root rot may first appear with yellowing foliage with a droopy appearance, and the roots will look brown slimy. Symptoms of root disease can vary depending on the primary pathogen attacking the plant but the term root rot covers all bases. This can make treatment complicated. What can work for one grower may not work for another but, never fear, there are ways to fight back.

Onset is more likely immediately after you change the nutrient solution in your reservoir as well as being more prevalent in younger plants. Thus, one of the first measures with seedlings is to only top-off the nutrient solution in your reservoir for the first few weeks after planting. Wait until the root system has had time to become well established before you do a full nutrient solution changeover. The roots will develop a biofilm of protective bacteria in that time, shielding your roots from those nasty pathogens.

Once roots are damaged and turn brown, they're gone forever - lost to the void. What you want to see is new pearly white to cream colored growth. Make sure the temperature of the whole system is between 18-20°C/64-68°F, and the nutrient solution is sufficiently oxygenated to tackle anaerobic bacteria. The solution should almost be turbulent with bubbles from the air stone. 

This is a pretty cool video demonstrating what root rot looks like at different stages of disease progression.


Now, what happens if you’ve completed those steps but you’re still getting root rot? Brown slime algae could be the culprit if proper reservoir conditions are in order.

Brown slime algae may well actually be cyanobacteria which are photosynthesising prokaryotes able to fix nitrogen. They can survive as unicellular organisms or band together to live in colonies, enabling the cyanobacteria to withstand much more harsh environments.

The slime covering your roots multiplies extremely quickly, enough to notice the difference over a 24 hour period. Beginning as a light cloud and odorless, and ending up like thick mucus with a yellow coloration.

It prevents the roots from accessing nutrients and oxygen, allowing parasitic oomycotes to thrive turning the roots brown with an odor of mildew or general rotting.

There are sterilizing agents available which will kill any cell it comes into contact with, however, it’s not going to be possible to continuously target all of the slime without considerably damaging your plant along with it or absorption of the bleach products. Both are less than ideal. Moreover, you’re killing any potentially beneficial microorganisms within the system and a lack of competition will only help the cyanobacteria.

Here’s where we get to the best natural remedy for root rot - brewing your own microbe tea.

How to fix root rot in hydroponics

The original recipe was written by Heisenberg but we’ll run through it all here. Additionally, the images we’ve collected come from Dustybowlz, where he’s gone through each of the outlined steps.

The first step is to physically clean the roots over a sink and remove anything dead and slimy. Soak the root bed in a sterilising agent for a maximum of 12 hours, Heisenberg recommends Physan 20 as a good product. All of your equipment should also be sterilised during this time.

The key to the tea is its diversity. The competition between this multiplicity of microbes ends up attacking the cyanobacteria from many different biochemical angles, not even the colonies can withstand.

There are several products you need to purchase to make your tea. It’s going to be brewed separately to the reservoir and then added later on. This works out cheaper and prevents also the cyanobacteria from consuming the energy source you provide in your tea which would lead to potentially explosive growth.

These products form the basis of the inoculation of your tea.

Aquashield (discontinued, read on for alternative): contains Bacillus subtilis, Paenibacillus polymxa, Bacillus circulans, and Bacillus amyloliquefaciens. This gives your tea a foundation of beneficial bacteria but you can replace Aquashield (it's been discontinued and replaced by Hydroguard) with any product containing bacteria of the Bacillus genus.

ZHO powder (discontinued, read on for alternative): contains Glomus intradices, Glomus aggregatum, Glomus etunicatum, Glomus mosseae, Trichoderma harzianum, and Trichoderma koningii. This provides your tea with a foundation of beneficial fungi but you use any product containing myco fungi (Great White is an alternative to Zho powder).

Ancient Forest: contains a huge variety of microorganisms, for example, over 35,000 species of bacteria and 5,000 species of fungi. You could replace Ancient Forest with any earthworm casting product.

You'll also need a black bucket or container to hold everything, one or two airstones to oxygenate the water, molasses to provide the energy for all the microbes, and two gallons of distilled water.

Picture of bacterial products red

Heisenberg makes his tea up to 2 gallons/9 litres of pure, dechlorinated water which can be bought as distilled water or filtered.

Two gallon bucket

Add one or two air stones to increase the oxygen content of the water, enough to make the water  is nearly choppy. This will help the aerobic bacteria outcompete the anaerobic bacteria, which are in a simplified sense the pathogenic species.

Air stone red

To the oxygenated water will go 15-30ml of Aquashield, and approximately ¼-½ a scoop of ZHO powder.

20ml of Aquashield red

Half a scoop of ZHO red

You incorporate the Ancient Forest/earthworm castings by adding a couple of handfuls to a sock or tights and tying the other end off. Dip the earthworm casting-filled sock into the water directly above an air stone.

Earthworm Casting red

Tights with EWC red

One tablespoon of Molasses mixed into the water will be the energy source required to activate the bacteria and fungi present. Only add molasses to this container and never the reservoir. Providing the cyanobacteria with delicious Molasses is only going to make the problem worse.

Molasses spoon red

The beneficial bacteria in the reservoir are going to be replaced regularly so, as helpful as they are, it’s necessary for them to starve for the greater good.

Leave the microbe mixture bubbling at room temperature for 48 hours. The number of bacteria and fungi within the container is going to explode, some will consume the Molasses directly and others will consume other organisms. A foam may begin to form, all is well.

Turbulent water red

After the broth has matured over the two days it can kept refrigerated for 10 days before needing to be replaced. You’ll know when it’s past the point of no return because it won’t smell good. Healthy tea smells earthy but bad tea smells literally like death.

One cup of tea per gallon/4.5 litres of reservoir nutrient solution. Every three days thereafter add one cup to top it up. Try and inoculate the root crown where new roots will grow from, the idea is for new white shoots to appear in time. The nutrient solution may end up cloudy but will be fine.

The cyanobacteria will disappear but the beneficial bacteria can still be used to maintain a healthy reservoir and prevent future root rot.

After-slime can occur, which presumably consists of dead cyanobacteria and will be harmless. It’s brown in colour but, again, as long as there are new roots growing you’re all good.

Remember to steer clear of using sterilising products in your tea. It’s pretty much all living beings in there and living things don’t like being doused in bleach.

The key to keeping your reservoir disease free is by being disciplined in preserving the proper reservoir conditions. To remind you, a well oxygenated nutrient solution with the air pump at one watt per gallon/4.5 litres, temperature within 70-75°F/21-23°C, and make sure zero light gets through to the solution which includes on any external tubing too.

Have you seen our other Articles on hydroponics?

The Basics Of Hydroponics  |  The Kratky Method  |  Types Of Hydroponics  |  Deep Water Culture  |  The Drip System  |  The Wick System  |  Lighting In Hydroponics  |  The Ebb And Flow System  |  Nutrient Film Technique  |  Nutrients For Plant Growth  |  Ventilation For Hydroponics  |  Growing Media Used In Hydroponics Hydroponics  |  The Best Way To Cure Root Rot  | How To Choose A Grow Tent | The Best LED Grow Lights | Everything You Need To Know About Nutrient Lockout | The Best Air Pumps For Hydroponics | The Best PH Meters For Hydroponics | What Mom Never Told You About The GH Dual Diaphragm Air Pump |


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