If you want sensitive, birdsnest would be a good test, and luckily its relatively cheap. It grows insanely fast when happy, but can die overnight. I have a collection of skeletons for house decoration and its all birdsnest.If you plan to get any softies from MACNA you should also get some to test. Zoas are the best indicator in my mind. If they are not happy they may live for a long time, but will not reproduce. Typically LPS dont care either way and I cant ever kill frogspawn, hammer, torch, etc.I wouldn't intentionally overfeed if you want primarily SPS. Softies are what like a little dirtier water. SPS still want some nutrients, but not enough to where you have to intentionally overfeed. Also, dont run carbon longer than you need to, it will remove many good things also.