Everyone's set-up with sinks and faucets and distances and heights is different so I think you just have to figure it out. I vacuum gravel while siphoning, take out 50% of the water. Then I run a hose connected to my faucet with a copper adaptor directly into the tank. I just check the temperature of the water coming out the hose and dip my finger in the remaining water in the tank and try to keep it about the same, usually I am off by a few degrees but not by much. I add Prime either before the refill or during it...Not to fussed about which. I have done a million water changes with this method and never had an issue. Buckets are a pain!