Maybe I'm just being paranoid, but I really don't want anything to happen to this tang so I'm posting.
20G high tank, black background on the back, no substrate, some PVC
joints for hiding places. I did a fishless cycle on this QT alone, and before I put the fish in, I did a 100% water change, and the water I added was from my main tank, 0 Ammonia, 0 Nitrite.
I learned the hard way to assume that every tang I buy has ich, so they're undergoing preventative hyposalinity treatment. I also gave a preventative dose of PraziPro before I put the fish in. I'm doing 20% water changes and replacing with freshwater every 12 hours, so it went like this:
Fish store water: 1.025
Saturday night: 1.021 (first WC
was right away)
Sunday morning: 1.016
Sunday night: 1.012
This morning: 1.009
All measurements taken with a refractometer, all water treated with Prime before it went into the tank.
They're getting nori and some red algae with garlic. Also, Saturday night they got frozen omega shrimp. Sunday night they got frozen brine shrimp. Tonight they're getting more omega shrimp and I was going to try giving them some frozen mysis too.
I picked up two tangs on Saturday: an Atlantic Blue Tang and a Blonde Naso Tang. The Naso is slightly bigger than the Blue, and made it known that he was boss. Aside from trying to intimidate each other, they did pretty well. I was ready with a barrier if they needed to be separated, and I watched them pretty closely. It didn't get violent, and the Atlantic Blue gave up trying to be boss and they actually got along OK. They both ate Saturday night. Sunday night they both ate the algae, and then when I gave them the brine shrimp, the Naso didn't eat, but Blue happily did. I thought it was strange, maybe the Naso was just being picky.
Tonight, I just gave them the algae, and the Blue went after it, but the Naso doesn't seem interested. Now I'm getting worried. I took some measurements really quick: Ammonia is 0 and Nitrite is 0, temp is 78. The two fish aren't bothering each other at all, really. The Naso makes it a point of flaring up when he feels like he needs to, but it looks a lot like yesterday when the just started being fine with each other. They are both active and friendly to me just like they were in the store. The only thing I can think of is that hyposalinity treatment is bad for Naso tangs, but I haven't been able to find a good resource on exactly what types of fish it's OK on, it mostly just says "use it for tangs".
Neither tangs shows any physical signs of weakness, disease, or stress. It's just the Naso tang not eating, and it happened so suddenly last night -- the time between when they got algae and the shrimp was 1-2 hours at most. Should I be concerned? What, if anything, can I do?