SInce I never know when I'll need to put my hand in a fish tank, I never use anything on my hands/arms that might cause a problem.
I regularly put my hands into tanks containing multiple venomous fish, some quite a bit more toxic than the lions, but I really don't worry as I always know where the fish are, and all of our fish are pretty tame, meaning they don't get sketchy when my hand is in the tank. In fact, there are a couple I have to gently shoo away.
As for eels, I've been bitten twice by a full-grown SFE...once I had to wait until it released me (I still have a couple of scars on my finger). The second time, my hand wasn't even in the tank...the eel poked its head out of the tank and bit me as I was changing a lamp in the canopy! There's no way it could have dismembered me...eels can't bite thru bone...their teeth are for grasping and tearing. They tear chunks of flesh off of items too large to swallow by "knotting", where they use their own body to pull against while tearing a chunk out of their prey.