HELP!!! Fish looks sick and i dont know what to do!!!

[appreciation]

ive been doing frequent water changes and today y nitrate level jumped to 40ppm and my yellow boxfish looks almost dead i need help i dont no what to do!!!

[Hookup]

a) photo would help
b) description of "looks sick" is needed
c) water test paramaters, and history if possible
d) other tank inhabitants
e) history of this fish, how long ago did you add him/her, was it eating, etc

[appreciation]

he died about 5 minutes after he started acting strange

[Julie]

Did your nitrate just increase to 40 today?    How much water have you changed and what size is the tank?
Sorry about your fish, any other inhabitants?

[kennyman]

sorry you lost a fish. I really like the look of box fish. Something else must have died in there and polluted your tank. It can happen fast  

[Hookup]

That's too bad... Sorry to hear he died.

[ray]

Imo,boxfish are quite difficult to keep.40ppm nitrate is not usually high enough to kill fish.Boxfish are known to secrete a toxin when stressed,the stressor can be as liitle as sudden movements,lights going on/off etc.If it released the toxin it can kill itself and other tank inhabitants.If this occurred running carbon and changing water may help prevent other losses.