First indication of trouble

[crna1]

What fish/coral is the first to give you an indication that a parameter is off before it shows up on a test?
Thanks!

 

[littlefoxx]

What fish/coral is the first to give you an indication that a parameter is off before it shows up on a test?
Thanks!

Nala my lionfish

 

[AstroCoral]

What fish/coral is the first to give you an indication that a parameter is off before it shows up on a test?
Thanks!

Ultimately it depends on the specific parameter that has changed. My green stem duncan is probably a good example, it will pull in with just about any change to lighting or salinity. It’s very resilient but it definitely will tell me when something has changed in the tank.