Why Biochar Is a Bad Idea in Hydroponics and Aquaponics

Read the updated version of this post here: https://zipgrow.com/why-biochar-is-a-bad-idea-in-hydroponics-and-aquaponics/biochar

What is biochar?

Biochar is charcoal created from plant matter.

Its a great option as a sustainable nutrient-stabilizing practice, but can cause problems when used out of context in hydroponics or aquaponics.

Here’s why: biochar retains nitrogen.

Biochar retains nitrogen

Biochar possesses many beneficial traits which can contribute a lot to sustainable, earth-healthy practices.

Unfortunately, the same thing that makes biochar a benefit to various agricultural and environmental methodsis a death sentence for hydroponic and aquaponic systems.

That trait is nitrogen retention.

In ecosystems that experience rapid or flash movement of nutrients (like parts of the Amazon, which is where the use of biochar originated), biochar can be mixed with soil to capture some of those nutrients as they move through the soil.

In that form, the nutrients – namely, nitrogen – are released and available to plants in the long term.

What people dont understand is that it works in tropical soils because its mixed with fat, with waste from the camp, with garbage, and it manages to hold on because its got high cation exchange capacity.

Biochar holds on to those nutrient well and it keeps them from from dissolving in solution and washing away.

Dr. Nate Storey“In the tropics, in the Amazon, 90% of all of the nutrition is tied up in the actual plants.

Almost none of that nutrition is in the soil because it just washes away. In this scenario, organic matter does a great job of tying up nutrients and making them available.”

Why biochar + hydroponics = a bad idea

Use biochar in hydroponics, on the other hand, nutrients are tied up unecessarily.

Dr. Nate explains:

Many people take it and dump it into their systems that they’ve been working on by adding compostor fertilizing. Then they dump biochar in, and it crashes their nitrogen, because the microbes start to break down that carbon and to do that they consume nitrogen. They consume nitrogen to break down the carbon, and its not carbon thats going to the plants.

A few weeks ago we got a call from a befuddled aquaponicist, with a good stocking density and a cycled system but no nitrates showing on test measurements.

After learning more about the system we discovered that in addition to her ZipGrow towers, she had a media bed filled with biochar as recommended by a friend. As her fish produced ammonia, her microbes converted it to nitrates, and the copious volume of biochar sucked up her nitrates rapidly.

Her plants, unfortunately,were now deficient in a primary nutrient, and theygrew stunted slowly.

The good news is that hydroponicists and aquaponicists don’t have a need for biochar.

Most hydroponic systems, and all aquaponic systems, are recirculated. (If your system is not recirculated, it should be.) Your nutrients have only one place to go: to your plants. You dont need to worry about tying them up in organic matter for long-term use.

People usually use biochar on a bad recommendation or with the logic that if it works in one place then it will work in another.

This one size fits all mentality is pretty common in alternative agriculture. In fact, when I asked Dr. Nate a few weeks ago about the worst aquaponics advice he had ever heard, he replied, People are always recommending you add biochar. Thats terrible advice.

Replace biochar with an inert media

ZipGrow Matrix MediaSo if you are using biochar in your system, its time to take it out.

Youll be delighted with the change in your nitrification.

If you have to replace biochar with another type of media, use an inert media such as Matrix Media.