Luck would seem to be a part of the equation, but superb fishkeeping probably has something to do with it as well, punch...and the fact that your clowns don't get ich validates that.
One interesting thing I noticed was that it lists male Bettas as sensitive to well water. Well water is described by them as being any tap water not from Michigan (column Q)
If I am getting the colums straight and understanding what they are saying......I disagree! I have seem Bettas kept in "true" well water and also numerous tap waters (most are).
I think that they mean w/o acclimation, but I'm not sure. I don't disagree with the fact that there are many discrepancies with the facts when this chart is read, but I think that it is overall a good tool (if taken with a grain of salt).
I used formalin (and salt) on my loaches (when first purchased) to be sure they weren't carrying ich. Formalin is cheap if you buy the full strength stuff (37% formaldehyde). Just an fyi. 1/2 dose initially, wait 4 hours and add another 1/2 dose. After that, you can add full dose for the remainding days.
Wouldn't want a crab as a familiar sitting on my shoulder, might pinch my ear...ouch!