I'm new to the hobby and had my tank for about 2 months now. I bought it off of someone on Craigslist 120 gal fully functioning with fish and all. With this being my first salt water tank I took a lot of the guys advice that I bought it off of and lots of online research. My question is I'm keeping the tank on the same water change cycle that the previous owner had 30 gals every 2 weeks. Was wondering tho if I should be doing maybe like a 15 gal change every week. All test perimeters are good just super OCD on making sure everything is ok cause seems like a lot of conflicting things that I read on the internet and makes me think I'm doing something wrong.