On average, I change 20-25 gallons every 2 weeks in 155g tank. Although, I think if you did half that frequency, that would still be sufficient. Keep in mind that the initial algae blooms are normal and will pass. Too many water changes with non RO water might even fuel it further.
I guess a good rule of thumb might be 10-15% every 3 or 4 weeks. The range of opinions you'll get though, will confuse you even further!!
