I used to do water changes about once a month, have been increasing it now to once a week, occasionally once every two weeks. On weekly changes I change about 40% of the water, if it has been two weeks 60% of the water. I use a bucket and siphon to pull the water and clean the surface of the soil, then run a small diameter garden hose from my utility sink in the downstairs to fill the tanks. The biggest issue is getting the temperature of the water correct. I use a y valve on the faucet so I get an immediate temperature reading, i.e. I don't wait for the water to travel through the whole hose, but I would sure like to source a temperature regulating valve. The entire process takes about 3 hours for me, cleaning the tanks, draining and filling so I tend to do them on the weekends.