I can only go off of what I have done, and I personally have never had a problem with it.As always, thank you Kaosu...
I've read conflicting arguments about this phenomenon, in which some hobbyists claim anything the carbon takes in and removes from the water -- i.e. bad stuff -- it will definitely eventually leak back in when the exhaustion goes too far...that's why I was asking you guys in here with such conviction; I just feared for the health of my fish.
Thank you for putting my mind at ease about it...
I could see it maybe causing a problem if you have medicated your tank...and used carbon to remove the medication...maybe?, but I rarely If ever use medications. this would be the only time i would worry and would remove the activated carbon after about 24hours once im sure the medication is out of the water ( ....but you can also remove medications with a few large water changes).