When soil ran out of nutrients, how do we handle it the best way?

[Phillipians]

Hahah actually i doubt many people actually buy used soil. Some would buy to lay the base as there is beneficial bacteria in it. I would lay at most the bottom most layer with a little bit but the rest is best to use new ada aquasoil. Actually i am a little puzzled why people bother selling 1 year old soil. Its out of nutrients... haha. But for the BB i think can get a little to lay the 10% at the bottom

[Urban Aquaria]

What other ways can the substrate be rejuvenated? Would buying old ADA soil be counter intuitive since those soils may be on the verge of total nutrient depletion?

Water column fertilizer dosing can usually supplement the nutrient requirements for most plants, even for heavy root feeders... the fertilizers do permeate into the soil and the plants can also take up the nutrients from the water too.

The other method is to increase the bio-load or feed the livestock more, so that they produce more waste which settle on the soil substrate where the beneficial bacteria there break it down into nutrients that the plants can use (aka Diana Walstad's "el natural" method).

As for used ADA aquasoil, the remaining nutrient content would depend on what density/type of plants grew in it (and the growth rate) and the length of time used. Buyers will just have to gauge the value of it based on information that the seller gives. Generally the longer its used, the cheaper the soil should be.

That's also something i'm wondering at. I notice a lot of people selling used ADA soil. I'm not sure if that's a good idea or is there something that other people do with it that I don't know? I mean how can you trust the nutrient contents of it without knowing how heavily it was used before.

Yeah, thats just what buyers have to factor in when they buy used soil... though there are also people who do want ADA aquasoil with most of it nutrients already used up. For example, shrimp keepers (they only want the pH buffering feature, but not the nutrients) or those who keep tanks with few plants but like the soil mainly for its looks.

That being said, ADA aquasoil has very high cation exchange capacity (CEC) which allows it to store and release large amounts of nutrients. So even if its initial nutrients are depleted, it is very easily rejuvenated by base fertilizers or root tablets/sticks, hence its lifespan can always be extended many times.