I used him as a source of information before I came here. The author to all of the pages is an older man and when he learned fish keeping a few decades ago most of the tank sizes he listed were generally accepted back then. Compared to a lot of the horrible sources you could find on the internet, his pages are pretty accurate and he has a wide variety of fish pages. You also have to keep in mind he owns a pet store, where is most cases the larger fish are traded in. He can't have a few 100g+ tanks on reserve just for fish that get traded in.