I have three large fish tanks and change 300 of gallons at a time at a time I actually run out of hot water before I am done.What I do is take a garden hose and hook it up to the slop sink in garage and run it to a 35 gallon pail,were I add salt and Seachem Safe it is a powder that dissolves in water 1kg treats 200.000 gallons of water it treats chlorine,chloramine ammonia and detoxifies Nitrite and nitrate. If you do not have a slop sink you can go to a plumbing store and get an adapter that hooks up to a regular sink faucet and makes it 3/4 for a hose to go on.I bought a 1/4 horse utility pump that I run from the pail to the tank to add new water,what is nice about this is you can adjust the water temperature without shocking your fish.Just make sure that you stay on top of it while filling pail,because i have been distracted before and I tell you running like a mad man when pale overflows is no fun.some people put the water right into there tanks and it works for them,But I have a lot of Chloramine in my water supply,so I rather do it in the pail plus it is easier to regulate the water temperature In the pail rather than going strait into tank.you can also use the pump to take water out of your tanks,makes it simple. Just do not put pump to low that it sucks up gravel.Hope this helps you out I have been doing it like this for years