Hi Melody -- I do water changes every week. I have an IO bucket that says it made 200g. It's bigger than a 5g bucket, but I'm not really sure of its capacity. I make water in that, drain a nearly full 5g bucket's worth from the 29 and replace it, and use the rest to change water in the 5.5. I'm not sure how much I change in that, but I'd guess a bit more than a gallon. It's probably about a quarter or maybe even a third of the water in the tank -- there just ain't much water in it with more than 15 lbs LS and 9 lbs LR, a heater, and a powerhead! I have enough extra water from the IO bucket to refill the skimmer after cleaning it.
--cn
--cn