The smaller your tank, the more often you need to change water. For 55G, I used to do 10 % water change every two weeks in the beginning. After 6 months, I only change once a month. Some people say "don't change your tank water too much for SW
hobby, let the water marinate". But my main concern was Nitrates. I had a green hair algae outbreak and my nitrates was off the roof. 8O
That's because I never changed my water for 2 months. Now, I decided, it never really save me time and effort by procrastinating on water changes. It only makes you spend more time and hassle when you do decide to water change after procrastinating for months. No easy way out of it, really. But I would suggest a 5-G bucket of water change for your 55G once every 2 - 3 weeks. That's a pretty decent water change suggestion.