Newbie here! Cycled 36 gal for 2 weeks. PH was 7.4, ammonia, nitrates and nitrites all 0. Put in 3 fancy goldfish. 1" to 3". Water and fish great for another week. Did 5 gal water change with some vacuuming. PH is 7.4, ammonia is between .50 & 1.0, nitrites and nitrates 0. Where did I go wrong and please help me on how to remedy this issue.