Hopefully I'm posting this question in the appropriate area. Say I'm doing a partial water change, 5 gallons of a 20 gallon tank. My assumption is that I only use enough conditioner to treat the 5 gallons of new water. It would seem to me if I treated all 20 gallons of water I would be using too much conditioner, especially since I'm doing these partial water changes every couple of days. Am I correct? Thanks!