[Delphinus]

There are SO many things we're exposed to, short of living in a bubble there's very little we can do to avoid exposure to something every once in a while. Just think of the sheer number of people who go to the bathroom without washing their hands. Ewww! I'm always amused at the argument "well I didn't pee on my hands." Yes, but, what's the last thing you touched? Now you use the door handle, and -I- have to use that same door handle .... I can't say it enough: Ewww!

As far as your tank though ... I've heard of people getting sick with salmonella like symptoms after accidentally swallowing some tank water trying to get a siphon going ... but it's completely urban myth to me since I probably heard the story "100th hand" not even "second hand." I dunno ... I'm a bit skeptical that it could be your tank. Isn't stomach flu usually a virus anyways? But if you're unsure, get yourself a pair of gloves and use those when you need to get into your tank. Actually the protection is then both ways, you don't risk getting anything foreign that may be on your skin into your water column.

But, BTW, wash your hands with soap afterwards ... just rinse really well..