Is he on a well or a municipality's water supply?
Is his water naturally hard or soft?
What is his average pH?
When Dino was teaching me about fishkeeping one of the first lessons was about keeping fish that thrive in the water you have normally. It cuts down lots of maintenance, and keeps the water as close to natural as possible. (Not having to pump it with the chemicals.)
Perhaps if we can find fish that thrive in your dad's water perameters, and if he keeps the tank well UNDERstocked with enough plants he might be able to loosen up on the length between water changes.
Lol, try to convince him a heavily planted tank with few fish makes for AWESOME games of hide-and-seek, which the fish love.
