So I took my 2 year-old son downstairs to see the aquarium, and he managed to beat on the front of it once really well. Of course, the Cardinal Tetras went ballistic in return.
I then chased my little guy around for about 5-10 minutes or so, and we ended up in front of the aquarium again. All looked fine until I looked at something stuck between the canopy and the acrylic front--a Cardinal! He must have jumped when my little guy beat against the tank.
I peeled it off the acrylic, and it wasn't moving or showing any signs of life. I put him in the water, and he was similarly lifeless. I grasped it between my thumb and index finger, and began moving him through the water as if it were swimming. I did this for about 30 seconds, and which point I noticed some pectoral fin movement. I continued for about another 10 seconds, at which point I let it go. To my amazement, the Cardinal started swimming on its own!
It's dorsal fin is still flat against its back--dryed out, perhaps. The good news is it seems like it's going to be okay.
That was interesting!