Really? Only 1tbps of ROX.8?

[MTF7]

So I just picked up some ROX.8 carbon and it’s my first time switching to it. Previously I’ve used chemmipure and Matrix from seachem, right now I’ve got a bag of Chemipure mini (rated 10g). I used the BRS calculator for my 13 gallon reef tank and came up with 1tbsp??? Is this really all I need? It seems like it won’t be anything 

[seabass]

Yep, that should do it.