Old substrate vs new substrate

[ninoboy]

This just crossed my mind. Which one is better? Is the old ones with dirts and stuffs in there better or new one from the bag. If they contain nutrients like iron etc, won't they be used up overtime?

[aquaverde]

For inert substrate (e.g., quartz gravel), old is better.
For hitek substrate (e.g., Flourite) it don't matter much.
For other hitek substrate (e.g. Florabase) new is better. They actually recommend replacing the substrate after a year. No money from me they'll be getting.

[ninoboy]

Thank for the info