Hi, I got a tank from someone back in February and have changed substrate, added fish, new lights....I used to test the water religiously and recently haven't been testing the water. I usually do 30-40% water changes every 7-10 days. I use tap water without any conditioners. I did test my tap water last month, and it has barely any traceable amounts of chlorine. Do I need to continue to do water changes as often?