Anything is possible?
I hand dosed directly into my tank for a number of months before adding an auto-doser to the sump (what a wonderful upgrade!) and never had a problem, BUT I made sure to dose directly into the highest flow portion of the tank so it's unlikely that I had a concentration of dosing liquid hanging around for any length of time.
If possible I would dose into the sump or at the very minimum make sure you are dosing into very high flow (powerhead perhaps?). Fish are not designed to inhale high concentrations of anything, they need a balanced saltwater that is consistent, so avoid putting them in that situation.