how many stones should i use?

i am setting up my first dwc grow in 2 18g totes, and i would like to know how many stones to use in each tote with my 15lpm air pump?

i use a 2.5lpm airpump and use a single semi-functional airstone without an issue in a 40L tote.

i have two 2x4 stones and wondering if 1 stone in each tote would be sufficient

I have almost the same set up but with 5gala buckets...I currently have two 3in stones in each one...good results so far

I would have at least have a 70lpm set up with 2 stones a piece for both the totes, but if it were me id spend a little more and get a 110lpm the more air the better and faster they grow