Found this on another site...
"Though pleasant to view and very playful fish, boxfish are not edible and do not make easy salt-water aquarium pets. If one kept as a pet should die, or even if is severely stressed, it will release toxins into the water which could quickly wipe out the entire tank population."
Here is a good reference page for them ... <a href="http://www.netpets.com/fish/reference/saltref/boxfish.html" target="_blank">http://www.netpets.com/fish/reference/saltref/boxfish.html</a>