Sadly, my dear little Firefish died.
I hadn't seen him out at all today, so I shined a flashlight in his little hole, and he was dead.
I don't know what happened, he seemed fine. I'm gonna check my parameters tomorrow when I have time, and do a water change. I also have to figure out how to get him out of the hole. I think it might have been because he wasn't acclimated properly. My mother kept making me do chores, so he was basically only temp acclimated, and then put in. Next time, I'm drip acclimating. Learned that the hard way...