Keeping in mind the various organisms that do grow in a tank, I can't help but wonder if you can get sick from your tank? I ask because my daughter's tank recently developed a sweet smell while going through a cycle. My wife "flipped" into a state of panic when she saw my daughter open the cover and smell the water. She was very worried about inhaling some organism that very well could end up in her lungs. Of course there are water born diseases like "legionaires disease" that can be transmitted by simply breathing the infected water droplets. Can a fish tank be deadly?