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The CEC loss of fired clay substrates (Manado etc.)

Simon Cole

Simon Cole

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I have been looking into Manado, and I am starting to suspect that it is has a relatively poor CEC, based on the degradation to clays caused by fire as mentioned in <this paper>.
Leca (expanded clay balls) I would assume could have rather similar chemical properties.

Does firing clay have a significant impact on substrate CEC? Is this impact so profound that the substrate might as-well be inert?
What percentage CEC is lost during firing would you guess? Could it be 99% lost?

I was going to use it with my emergent plants. I have used it a few times before. All thoughts welcome.
Sorry if this has been asked before. Thank you :)
 
I think you might be right. Manado is an expanded clay aggregate like Leca, which apparently has a very low CEC.
Just out of interest, have you come across the table below ? Published in Planted Aquaria, summer 2000.

1691141184969.png
 
Hi, I have tried the brown one. I have never tested it, but I would consider it inert, just more easily colonized by bacteria etc than colored quartz. If you want cheap high CEC substrate for emersed cultivation use Akadama.
Manado used to raise GH at the beginning, and I found it too light for planting in aquarium.
 
Simon Cole said:
I have been looking into Manado, and I am starting to suspect that it is has a relatively poor CEC, based on the degradation to clays caused by fire as mentioned in <this paper>.
Leca (expanded clay balls) I would assume could have rather similar chemical properties.

Does firing clay have a significant impact on substrate CEC? Is this impact so profound that the substrate might as-well be inert?
What percentage CEC is lost during firing would you guess? Could it be 99% lost?

I was going to use it with my emergent plants. I have used it a few times before. All thoughts welcome.
Sorry if this has been asked before. Thank you :)
Click to expand...

If you want higher CEC, standard aqua soils are pretty high - if you want it without nutrient loading, shrimp soils are pretty good.

If your emersed planters are in an aquarium, and are suspended up in the water column (on the tank walls etc), I'm not sure how important the CEC levels of the substrate is, as nutrient enriched water (assuming you will be dosing nutrients) gets exchanged through the substrate fairly rapidly I imagine.
 
Hanuman said:
Not really. Akadama has a moderate to low CEC which usually tops around 25meq/100g depending the souce. Aquasoil and some other substrates have a higher CEC which usually go up to 50meq/100g or more.
Click to expand...
Oh, it could be. I have recently set up two tanks, one with aquasoil and the other with akadama, both without CO2. It's not about CEC, but I have noticed that Aquasoil seems to lower pH too, not only KH, while Akadama lowers the KH, but then you have to dose something that lower the pH.
Anyway, well... I said cheap substrate. I have paid akadama 1,43 €/L, while aquasoil 3,8 €/L or thereabouts. I think that Akadama is fine considering this, though I would not consider it for medium-high planted tanks or frequent rescaping. For emersed cultivation, I don't mean paludariums/vivariums and so on, but something like pots or greenhouse box, aquasoil is just a waste of money.
 
ExcitableBoy said:
but I have noticed that Aquasoil seems to lower pH too, not only KH, while Akadama lowers the KH, but then you have to dose something that lower the pH.
Click to expand...
All price considerations aside, Akadama is basically deprived of anything or nearly anything. That is why when you use Akadama in a tank you ought to preload it with minerals prior using it else you will see big swings in GH-KH. It is simply sucking anything it can from the water column.
Most aquasoils on the other hand are already loaded with all sorts of minerals but also with humic acids among others which also buffer the water, reducing KH and subsequently PH.

If you want to know more about akadama in planted tanks I suggest you have a read at this excellent thread: Akadama - A cheap substrate
 
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