Randy Holmes-Farley
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My Tank Thread
FWIW, if folks are concerned about different depletion rates, there's no reason you cannot use proportionally less of the one that depletes more slowly so that they effectively need to be replaced at the same time. 
The flow rate issue is more complicated, but GAC will work at any flow rate you want, it just may be somewhat more effective at cleaning the whole tank if the flow is higher than might be optimal for GFO tumbling.
The flow rate issue is more complicated, but GAC will work at any flow rate you want, it just may be somewhat more effective at cleaning the whole tank if the flow is higher than might be optimal for GFO tumbling.
