Hey all, I have started my aquarium and have had it running over the last week with three small gourami's and would just like an opinion of when to do my first partial water change my tank is 130 liters it is an Aquaone i have plenty of plants and two pieces of driftwood and three rocks and have a PH of 6.6. I do not have a test kit just a pH kit. Any advice is great thanks !