I shoot for 10-20ppm Nitrates anything higher than 20ppm I do a water change accordingly and anything lower than 5 I add Kn03. Depending on your tank setup, lighting, co2?, substrate, plants, fish etc. you may have to add nitrates.
Just to touch on canister question. The nitrifying bacteria grow on the bio media in your filter (also your substrate rocks etc.). Providing you have enough media and flow to convert all of the ammonia and nitrites to nitrates anything past that will not make a difference other than creating flow and more space for bacteria to grow should your bio load increase. There are 2 ways (maybe more) nitrates will be removed from your tank water.
1. Water changes
2. Nutrient uptake by your plants.
If you have fast growing plants with high light and densely planted and small bioload chances are you will actually have to add nitrates.