Activated Charcoal as substrate

[keddre]

This is more of a theoretical question then a "I want to do it question". I was looking at my activated charcoal that I haven't used on up-teen years and wondering if it would work as a fertilizer or laterite replacement in a planted tank? My thought process is that at the beginning it would add zero value, but as it absorbs stuff in the water, it could become a thing that roots could latch onto the pull that "stuff" out; more of a long play, and not an instant benefits thing.

Has anyone played with this idea before? My understanding is this is how clay works, so it would be the same concept with a more expensive item.

[Guppysnail]

I cannot answer your question but this is an interesting idea. If you try it I do hope you will journal and share your experience.  

[Odd Duck]

I have heard of people putting in a thin layer in layered substrates, but have zero experience using it.  I would expect it to adsorb many different things, but I can’t give meaningful advice on safety or efficacy.  Did you try searches here and on other planted tank forums?  That’s where I’d start.

[keddre]

On 3/28/2022 at 11:11 AM, Guppysnail said:

I cannot answer your question but this is an interesting idea. If you try it I do hope you will journal and share your experience.  

I may give it a shot with a spare 20 Gallon, I have . Maybe do three different sealed pots with gravel, capped dirt and capped charcoal

On 3/28/2022 at 11:50 AM, Odd Duck said:

I have heard of people putting in a thin layer in layered substrates, but have zero experience using it.  I would expect it to adsorb many different things, but I can’t give meaningful advice on safety or efficacy.  Did you try searches here and on other planted tank forums?  That’s where I’d start.

I did not thing about that, but will give it a search. Searching old posts is a three brain-cell idea and I'm still stuck with two lol

[sumplkrum]

I wouldn't use it as a substrate by itself because it doesn't really have a 'heavy' consistency for holding plants. You'd most likely want to mix it with something else.

Another thing, if it's been in storage for a long time, be careful that it hasn't absorbed anything accidentally. If the container isn't in great shape who knows what it's absorbed.

Lastly, if you add it to a tank it's going to suck nutrients away from your environment. Once it fills up, it'll slowly leach out. If charcoal is your main substrate that will probably be a big swing affecting your parameters and possibly causing a crash.
I'm wondering if it might be better to soak the charcoal it in fertilizer beforehand, then add it to substrate in small amounts as a fertilizing agent. That way you'd have a more controlled nutrient release and can measure the effects over time.

[Odd Duck]

On 3/28/2022 at 11:51 AM, sumplkrum said:

I'm wondering if it might be better to soak the charcoal it in fertilizer beforehand, then add it to substrate in small amounts as a fertilizing agent. That way you'd have a more controlled nutrient release and can measure the effects over time.

Interesting thought, the pre-soaking.  The biggest issue I see with charcoal is floating.  Pre-soaking might reduce that issue but might not eliminate it.  Freezing the soaked charcoal into ice cubes might be one way to get it deep in the substrate like home-made, frozen root tabs.

[Ken Burke]

I would not use it alone, but maybe a thin layer under a gravel/sand bed could have some benefits.  Maybe.  

[lefty o]

i think it would be a poor choice. how i understand how carbon works is, it absorbs things until it has absorbed all it can, and then it does not give back up what it has absorbed. that added to the fact it will continue to break down in size, so you will eventually just end up with a black paste. ever notice all the dust that comes in carbon, well it wasnt always dust. food for thought. if you do go ahead and use it, keep us updated so we know how it does work.

[keddre]

On 3/28/2022 at 12:51 PM, sumplkrum said:

I wouldn't use it as a substrate by itself because it doesn't really have a 'heavy' consistency for holding plants. You'd most likely want to mix it with something else.

 

That is a good point, I was thinking capped, but a charcoal/gravel mix with a gravel cap makes more since (if I did this)

On 3/28/2022 at 12:51 PM, sumplkrum said:

Another thing, if it's been in storage for a long time, be careful that it hasn't absorbed anything accidentally. If the container isn't in great shape who knows what it's absorbed.

noted

 

On 3/28/2022 at 12:51 PM, sumplkrum said:

Lastly, if you add it to a tank it's going to suck nutrients away from your environment. Once it fills up, it'll slowly leach out. If charcoal is your main substrate that will probably be a big swing affecting your parameters and possibly causing a crash.

I wonder, because if it's buried under gravel how much would it actually pull from the water column, and the leach out vs. root uptake speed. I guess this is why smart people have test tanks and not just show tanks

On 3/29/2022 at 12:11 AM, lefty o said:

you will eventually just end up with a black paste. ever notice all the dust that comes in carbon, well it wasnt always dust

I wasn't aware of this. I knew it would break apart from friction together (bumping, shaking, gyrating), but didn't know it could simply break down while being mostly stagnate.

 

On 3/29/2022 at 12:11 AM, lefty o said:

if you do go ahead and use it, keep us updated so we know how it does work

I most likely won't, at least not in the near future. I like to just sit around and come up with half-bake, but not totally uneducated ideas

[anewbie]

My question is why use activated char. as a substrate or in the substrate? The life of the stuff with regards to absorbing organics is fairly short....

[Guppysnail]

You could do your fertilizer soak and put it in a small bowl on a windowsill with a root plant as an easy test run. 

[gjcarew]

I've used it before as part of a substrate that consisted of layers of osmocote, activated carbon, worm castings, Mexican red clay, and capped with ADA Amazonia. With such an elaborate substrate it's tough to say exactly what benefits the carbon brought vs. the rest of the ingredients. That said, plants grew like MAD in that tank, especially rotala species. The only reason I don't do it anymore is because it makes a bit of a mess when you have to uproot the plants to trim them. The tank with this crazy substrate is below.

There is a long history of the use of of carbon/charcoal for growing plants. One of the best examples is terra preta, where natives of the Amazon created a nutrient dense, rich soil for agriculture by mixing biochar (essentially activated carbon) with bones for minerals, manure, and broken pottery (contains iron). These soils are still much richer than the surrounding Amazonian soils 500+ years after they were introduced. Here's a scholarly paper on the subject.

Activated carbon on its own will do nothing for the plants. When "charged" with macronutrients, micronutrients, and minerals, it can act as a long-term nutrient storage that will not get diluted in the water column. It has a higher cation exchange capacity (what allows it to "grab" nutrients) than any other material I know of. The easiest way to charge your carbon would either be to soak it in Easy Green or add Osmocote to the bottom of the pot you're planting.

Tourmaline BC is a substrate additive sold by ADA. It is simply a mix of bamboo charcoal (the BC) with powdered tourmaline, which is a source of minerals.

 

[DavidTheGreatAndPowerful]

It would work pretty much how you think it would.  Except you need large ph swings to get the carbon to release some of the nutrients.  Some people use it in terrestrial plants for that reason.  With that being said it would not be a good choice because it would float, it is expensive,  and the ph swings would be bad for the fish and plants.  A better choice would be Safe t Sorb, turface, or cat litter because they do not float, they are cheap,  and they do not need large ph swings to release nutrients for the plants.  I have only use Safe t sorb, and it worked great for my tanks they are still running after a few years.  You do need to "charge" it first though, and I would recommend waiting about a month before adding fish.  I also prefer a small cap on it like an inch or less.

Edited March 30, 2022 by DavidTheGreatAndPowerful