Police say the office manager at Tri-State Neurological Surgeons found about 30 fish dead when she came to work on Jan. 16.
Police say they don't have a suspect, but are treating the case as one of criminal mischief.
The owner of a local tropical fish business says he adds a small amount of iodine to the 250-gallon tank because some fish need it to survive. But after the fish died, the store owner says he discovered the bottle was empty, meaning someone put several times the proper amount of iodine in the tank.
