So.i always wash and dry my hands before I put them in the tank, I'm a mechanic by trade and work with lot of harsh chemicals.
But with that said I think it's more about leaving things alone than actually having your hands in the tank.
Example #1: I decided I didnt like where a colony was growing, so i decided to move it.. (dumb idea) so instead of the colony breaking off the glue mount the while rock broke free of the epoxy holding it to the rock below. Causing an avalanche of rock.. yes knocking frags free and damaging corals on it's way down. Of course now being to fix it made it worse, stirring up the tank, ******* everything off.. get it all back together (never looks the same) lost 3 frags, they're just gone. 2 died the next day and the damaged ones had to be fragged. And to top it all off I never moved the colony I originally wanted to....SHOULDA HAD A BEER I STEAD OF PUTTING MY HANDS IN THE TANK!
example #2, did this years ago, couldn't find a fish I recently bought do I went searching. Dumb. Again stirred everything up scared the crap out of everything and destroyed my aqua scape. And still didnt find the fish... 2days later it came out... SHOULDA HAD A BEER AND ENJOYED THE TANK, INTEAD OF PUTTING MY HANDS IN THE TANK! Lol
So that's my thought on the subject. Keep em out, but if you do make sure they're clean.
Definitely agree with figuratively because without a doubt there are routine maintenance that needs to be done on a tank that can’t be done without putting your hands in a tank. With that said use common sense and wash hands thoroughly before and after. You can definitely get carried away with never being happy with the tank and putting hands in there making routine adjustments before the tank is fully stable. I believe this is why so many beginners fail their first year of reefkeeping. I believe that once your tank is established and stable, you are less likely to “need” to daily put your hands in the tank as you would the first year. This is my belief and if you do, routine “weekly” water changes can help correct any minor issues before they grow to be larger ones. As they say less is more.Depends if you mean this literally or figuratively? I suspect most people think of it literally (skin oils, unwanted chemicals, etc.). I think of it more figuratively in that you should let your tank do it’s thing and not be changing things around in there too much. Other than placing the mag cleaner wet side into the tank weekly my hand/arm rarely goes into the tank. Really just the occasional prune, coral addition, or replacement of something that got knocked over.