LECA is quickly becoming obsolete. Even hydroponics shops are having trouble getting it in. From my conversation with the owner of my hydro shop, it's being discontinued.

Weight is only a concern if you plan on moving the tank otherwise, it's really not an issue provided you have a decent stand

As far as biological filtration, there is more bacteria in the substrate than in the drainage layer for filtration. Not to mention that the water below the substrate is drained off regularly, so bio filtration is actually wasted down there. Don't get me wrong, it helps keep the water from getting stagnated quickly, but it's not my first consideration when choosing a medium for the drainage layer.


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