I have had SW for 11 years and have finally figured out the things I was doing wrong only because of advice that I followed from limited sources.
These are big mistakes made due to listening to advice from limited sources - I wish I had known of and joined a club all these years ago!
A=Advice
M=Mistake
C=Changes you've made
A: You only need to test pH, amonia, and nitrIte (note the capital I)
M: I wasn't testing for nitrate, which subsequently ended up being high for probably many years.
C. Now I am testing for nitrate.
A. The best substrate is crushed coral.
M: I used CC which turned out to be a major nitrate factory, and since I was told I didn't need to test for nitrate, I had no clue.
C. When I DID learn what I was supposed to be doing, and knew having the CC was causing a problem, I removed it.
A. Change 1/3 water 1x a month.
M: My opinion, which is based on the nitrate problem which I didn't know I was having (because of above bad advice), and the fact that the nitrate caused my tank to suffer all manner of problems with alga and cyano, is that 1x a month is NOT enough.
C. I am now doing weekly water changes.
A. Salt should be between 1.017 and 1.020.
M. Well, fortunately I wasn't keeping anything that the low salinity would kill.
C: Now maintaining 1.025.
A: Arrow crabs are non-aggressive.
M: Putting the creature in my tank only to find it in the process of eating my fish.
C. Not putting things in the tank without first studying them.
So, anyone else care to share?