04-07-2006, 01:59 AM
Join Date: Jun 2004
Some substrates lose their punch over time. I understand that ADA substrates come with a recommendation that they should be changed periodically. Soil substrates and other substrates with a substantial organic fraction can change over time. People might replace them to get back to the original characteristics.
I don't know of any reason why a gravel/laterite substrate should need to be changed. I have had gravel substrates in place for 15 years without problems. But then, changing out the substrate and seeing the effect could be fun.