Okay this might seem like a stupid question but I am just curious. I have been told you can't put straight tap water in your tank without decholrinator. I have seen these phythons that everyone is talking about and takes the water chlorine and all staight from the tap. Would that not logically kill the fish or am I confused? Is it only for water changes 25% that you can you do that for? I was curious cause right now I have a 22gallon bucket that I use for water changes. It was fine when I had only my 38 gallon and 20 gallon but I have inherited a 60, 40, 38, and a 20 so if this is not correct about the fact that you have to dechorinate all the water before it goes in the tank will make a major difference in my sea of tanks.

When I do water changes I put the dechlorinator into the tank before I add the new water.

I use a hose for filling, another for draining. I've squirted in dechlor before, during, & after. Doesn't seem to make much difference.

The chlorine & chloramine in tap water isn't deadly toxic to fish, it is an irritant though. It is deadly to bacteria, meaning it will kill off your bio filtration. Even this doesn't occur instantly, I've waited half an hour after a 50% water change to add dechlor, without a problem.

i always add the dechlor before the water, never tried it after the water but i think as long as you got it in, in a timely fashion it wouldn't hurt. i have never had a problem.

I also put dechlorinator in the tank before new water.

i use a hose from my kitchen sink to fill my tank with water about the same temp as the tank water and then put the chems in.

though i've heard that i shouldn't use the hot water tap to make it warm cause of the copper pipes, but sofar it hasn' done anything to the fish.....