Sleeper Banded Goby Death Help?
So, I bought two new saltwater fish yesterday. One was a 2 1/2" Six Line Wrasse. Some other guy was going to buy it, but let me take it instead. And today, day 2, he is doing great. The Yellow Tang was bullying a little initially, but today they're getting along great!
The other fish was a Sleeper Banded Goby. Now, when I asked about it, the fish lady told me it was a Dragon Goby. But I had my doubts, and a quick Google search confirmed that this was no Dragon. But, seeing as they both accomplished the same task, (and I would be getting a $25 fish for $17 XD), I bought him. Now, both of these fish were housed in the same tank at the store. According to the fish lady, the Goby was sifting and doing great before I got him. And after 2 hour of acclimation, he swam into a cave and disappeared. Now, as you know, Gobies usually hide for a while when you first get them. But this morning I found him sitting in the open. I was confused, but didn't question it. Sadly, no less than an hour later, he was being swept around by the current, dead. "So," I asked myself. "What could've possibly killed my fish?" He had no signs of an attack, so that was out. My PH, salinity, and various other levels were fine (granted, my nitrate is crazy high, but my other fish are fine. Even breeding no less! And my next water change is this weekend). So that was out. And it couldn't be that my tank was just too different from the pet store, because the wrasse was doing fine. (And no, he had not sifted into a substrate bubble. He hadn't sifted any sand yet). So I called the pet store and explained my problem. I wasn't mad that I had bought a crap fish. It was the fact that I had lost yet ANOTHER Goby! (SERIOUSLY, why do they keep dying?!) But the lady was understanding, and told me that the next sifting goby she got in was mine.
So, my question is, what could've killed him? Any ideas?