Okay, so after this morning's scare, I ended up rearranging babyfish's tank. :D He was cupped while I did, because I didn't want to risk hurting him. I took out the silk plant, changed what pot I was using for a cave, and added a few live plants. I also took off the lid, and replaced it with some clear binder sheets with air slits cut into the top. Also brought in a desk lamp and put a 14watt daylight bulb in that.
And this afternoon he got three new MTS buddies. :D
And that explanation of what is meant by 'rays' was really handy! Now everytime I go in, I try to look at babyfish's tail rays. XD So far I only see two, but his fin is still really small. I can barely see with my eyes, and I know my camera can't pick up more detail through the aquarium. Even after 10 days, his tail still has that scalloped look. Isn't it supposed to come and go as their fins grow?