This site, intending to bring proper goldfish care knowledge
to the average goldfish keeper will not go in depth into certain areas.
If you do wish to learn more (and you should) visit these links.
http://www.goldfishinfo.com
An excellent site with bounds and bounds of information. Although it
is heavily cluttered and hard to read, stick with it as it has just
about everything there is to know about caring for goldfish.
