That book is available through amazon. I noticed there was nothing about a skimmer listed in the index of the book, I don't know if it was part of filtration or not. I see where it lists a hydrometer but not a refractometer.
I know a few people that actually use ocean water in their tanks however it is tested regularly and if there is anything wrong with the water in it is off until it clears up.
Back in the good old days of stainless steel frame tanks and slate bottoms I use to get water from the river for my freshwater tanks today I would never go to that same spot to get water because of pollution. It was probably a good thing I grew up in ND where all we had was freshwater.