This is Hi-Fi

OK, this is ridiculous.

Fri 6:30 PM: I bought 3 Blue Chromis.
Sat 9:30 AM: I feed the fish and all 3 Blue Chromis are there.
Sat 4:00 PM: I add my last bag of sand to the tank. All 3 Blue Chromis are there when I start, and I think all 3 are there when I finish (I don't think I accidentally buried one since they're pretty fast and they swim near the top).
Sun 11:59 AM: I wake up and there are only 2 left. I look in the overflow and I don't see anyone in there. I quickly check the sump and I don't see anyone that has fallen into the drain. Grr.
Sun 8:00 PM: I feed my fish and see there are 2.
Mon 9:00 AM: I'm down to 1.

Where are they going???