Laticauda;4794316; said:If someone that owns a gravel-bottom tank, and does not adequately vacuum the poop/fish food/sludge out of it, then it creates a very large volume of organics to accumulate. In this situation, even with 100% water change, the nitrAtes will still be high. That is why you HAVE to vacuum your gravel, and HAVE to bang out (or replace) mechanical sponges/pads in order to keep your water healthy/clean.
This is because of lack of proper maintenance, not because of gravel. The same can be said of someone who does not clean their filter frequently enough.

