Weekly partials is the only way to go IMO. I do about 40% on my ten gallon and 30% on my 30. It all depends on what you want your nitrate levels to be at. If I was overstocked I would do 50% weekly. If you have to do more than that you are probably overstocked. My nitrate levels never measure above 5ppm in the ten and the 30 never registers above 10 ppm. Both tanks are lightly to moderately planted. I gravel vac every part of the substrate I can reach without disturbing the plants every week. Once a month I'll move the rocks/driftwood and vacuum underneath there too. The result - consistent water parameters (ph, gh, and kh) and healthy fish. Before I did this I killed at least two fish a month and sometimes one a week in the early months of the 30 gallon. I haven't had a death in the 30 since January and only one death in the ten since I started it 3 months ago, and that one was last month. I know all that for sure because I'm anal and keep a log spreadsheet of both tanks
.