Ok, this may sound odd, but I have noticed a contradiction between
changing water to remove accumulated nitrate and then adding nitrate
in various forms via some type of fertilizer. What part of the big
picture am I missing?

Plants. If you have a high-tech, high-light tank with a lot of fast-growing
plants, they will use up nitrate faster than the fish and bacteria can generate
it. So people with such tanks have to add nitrate.

For the average tank, with a few slow-growing, low-light tanks, or none at all,
the nitrate tends to build up, and must be removed with water changes.


Leigh

http://www.fortunecity.com/lavender/halloween/881/