I have two 45 gallon plastic barrels in the closet of the room where most of my tanks are. I have an air pump with two outflows in there, so one big airstone per barrel. Whichever barrel I'm going to use next, I have a heater attached to large, cheap airstone which weights it down in the tank. I only use a 50 watt heater, but by the time I'm ready to use the water, it's up to the same temp as my tanks. I submerse a 650gph water pump with about 10' of water line attached, at the end of which I installed a ball valve so after I turn the pump off remotely I can close the valve so I can set the hose on the floor for a minute without the water siphoning out. The pump is plugged into a remote control plug-in ( like a clapper, only with a remote. Hard to clap while busy changing water :wink: ). I python vac/wc then refill with the pre-heated, chlorine free water. When a barrel is empty I just pull the pump and heater out and plunk it into the other barrel, then refill with python after I've sucked some bleach water through it for awhile first, then a bit of water containing dechlorinator ( small 97 cent mop bucket from walmart is what I use for that).
I got the remote control plugin from walmart for like 7 dollars, red tagged. I keep it in the closet so nobody bumps it and has my pump running with the valve closed. I also installed a cheap metal hose-hanger in the closet to place the water line on when not in use.
My city uses chlorine only as well, as I found out from the water dept.
For the tanks downstairs, I didn't think setting up another set of holding tanks would be very cost effective, so I just use Prime for those.