A link from the 70s? Sorry, it's called a book.
Fish and Invertebrate Culture 'Water Management in Closed Systems'; Dr Stephen Spotte; Wiley-Interscience Publishing (ISBN: 0 471 02306-X).
Wasn't trying to be anything except informative. Figured the 'old school' and 'decades' references would have dated the subject matter. Sometimes I fail to consider just how long I've been in this hobby compared to others.

