I was thinking if its alright to use higher tds tap water which is about 270 in my area for cycling of a new aquarium and once say after a couple of weeks when the cycling is complete can I use water from an RO plant with less tds before adding discus. Will the change of water with less tds from 270 to say 50 kill the beneficial bacteria growing in canister media and rocks or will the change of water tds not kill the bacteria. Secondly how do people measure nitrates and nitrite with API kit when water has tannins. The water is light brown and comparing the color of test tube with chart becomes difficult.