Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
No set amount is correct.
Non-planted tank: Monitor the NO3 and do enough water changes (volume and frequency) to keep the NO3 no higher than 20 ppm.
Planted tank: Depends on the fertilizer program, but if you are following the EI method, then it calls for 50% once a week.
If you modify that, you may be just fine with smaller water changes.
Walstad style tanks generally get much smaller water changes, infrequently.