Depends upon the fish.
Most will usually just swim away from you. My Xilo pair, Escondido pair, and a couple others (even convicts and little crypto's) will all bite me if they are defending a spawn though. There are a few rare fish that will come up and bite you anyway. I wouldn't trust a Dovii or chancho. Most others I wouldn't be concerned unless they are breeding.
Most will usually just swim away from you. My Xilo pair, Escondido pair, and a couple others (even convicts and little crypto's) will all bite me if they are defending a spawn though. There are a few rare fish that will come up and bite you anyway. I wouldn't trust a Dovii or chancho. Most others I wouldn't be concerned unless they are breeding.