Look at my build thread (see signature). My sum is very large.
If your sump is oversized I don't think you need calculate water change volume the same as a traditional setup. The bio load does not change with the size of your sump.
There are things you do need to consider though. Heating and cooling for sure and possibly skimming. Although skimming can be debated based on my prior bio load statement.
I am going to do a lot of water changing experimentation when my system is up and running.
If your sump is oversized I don't think you need calculate water change volume the same as a traditional setup. The bio load does not change with the size of your sump.
There are things you do need to consider though. Heating and cooling for sure and possibly skimming. Although skimming can be debated based on my prior bio load statement.
I am going to do a lot of water changing experimentation when my system is up and running.