Is it safe to put your hands in a fish tank without gloves?

Ok...first of all, I own an aquarium and my dad is a fish genius. Don't ever put your hand in there if it has lotion, perfume, soap, or any type of substance. Not even food! Power never has to be turned off to put your hand into the tank. Just don't try and touch the fish because it can stress them out. Hope this helps! Cheers -Sarah