10 gallons on a 46 with 20 sump, never added it all up and figured out the percentage, i do every other saturday. sometimes i miss one, but not very often at all. and if im going away for a day or two, ill do one before just to make sure everything is as clean as it can be.
I did 10% water changes once every 2 weeks. Then had a bad brown algae prob. I got real sick for months and never touched my tank. I started feeling betterhen one day looked at my tank and it was crystal clean. no brown junk either. This made me realize I was keeping my water too clean so Now I do it maybe once a month, usually about a 3rd of the tank. If it is wrong or not, it works
10g every week. this is on a 170g system. this is all i need to do to remove all of the detritus from the sump and faux SB. i could prolly get away with a 5g, but my semi-auto water top off does not work as well with only 5g in it.