Hi all,
Does this have a lifespan or will it continue to absorb nutrients from water forever?
All active substrates will stop being "active" after a while. They don't lose the ability to exchange cations, they've just reached an equilibrium point with the tank water.
Typical aqua soil has a high CEC
That is the real point CEC is "Cation Exchange Capacity" and that is exactly what it is, the <"
ability to retain and exchange cations">.
When you start with something like <"
Akadama"> or <"
sphagnum peat">, all the cation exchange sites are initially filled with a proton (H+ ion), because they have formed under conditions of high rainfall. These will then be exchanged for more strongly bound multivalent cations from solution (your tank water).
If you start with a "blank slate" substrate you can load it with cations by soaking it in a strong solution of ions, I assume this what ADA do when they make <"
ADA Amazonia">.
The first time I used the moler clay "Tesco Cat Litter" I rinsed it in our tap water (hard about 18dGH/dKH). It didn't get rid of the smell, and it meant that all the exchange sites were filled with Ca++ and HCO3- ions, so it raised the pH and hardness of the <"
rain-water tanks I used it in">.
If I'd used it in a tank with our hard tap water, it wouldn't have had any additional effect effect, because the ion exchange sites would already have been in equilibrium with the water.
The next time I prepared cat litter I just left it outside in the rain for ~ six months. I could have soaked it in an acid solution (acids are defined as "H+ ion donors"), but I would also have added anion.
If I try it again I might have a go with hydrochloric acid (HCl) first, followed by some time (couple of weeks?) in the rain and see what happens then.
cheers Darrel