Best substrate in a sump with caulerpa?

[Joshsmit56001]

I was just wondering what the best substrate would be in a sump with caulerpa. I want to really get the natural filtration working and not really on mechanical filtration as much. What else other than a refuge in my sump can I do to get a lot of natural filtration?

Thanks,
Josh

 

[gooyferret]

LR and LS will give you the best biological filtration.