There is a huge variety of opinions on water changes. For a brand new tank that I was trying to control ammonia on (not typically an issue in a more established reef) maybe change some every few days for a little bit? Test your water often, it will let you know what it needs. Start with 10 gallons (ASAP) and test again. See where that puts you and go from there. Long term you won’t need to change water nearly as often, or as much. It depends on what sort of filtration, dosing, and feeding schedule/bio load you have. Personally, I change 5g of water every 14 days on my 28g, but in 2 separate changes so as to minimize swings and maximize nutrient export. Some people will go multiple weeks or even months without water changes and everything in between, but that is in established systems that already have a good biofilter established. Definitely don’t add any other fish and keep feeding to a minimum for a while, and hopefully everything will be fine!
Oh, and I hope that didn’t sound like Greek. Ideally when you do water changes you don’t want to change more than 20-25%, but in this case it’s much more important to get that ammonia down.
