My fish also love the new water! I freaked out a while ago because one of my sensitive fish was playing in the new water coming out of the tap, and he is supposedly a sensitive one! Well, he does it all the time, and he is fine. The fish in the other tanks also won't stay away from the new water

.
As for using dechlor with the Python system, you just put the dechlor in and then fill with water. But if you are using buckets, put the dechlor in the bucket before you dump it in. I usually put it in while the bucket is filling.
Sounds like you are getting the "multiple tank syndrome" like we all seem to have too!

I started with one tank in August, and now I have 5....
My fish also go nuts for the peas! They would eat them everyday if I let them
Hard water is not good for some fish. What kind of hardness do you have? In my water, I have quite a bit of lime and calcium, and it has never bothered my fish, and I don't use anything to treat it, except Prime Water Conditoiner.