Alright! I'm stumped here, it's like playing a game of clue when you've lost half the cards. Here's my dilemma: I had a heavily planted (plenty of places to hide, but I could find everything when I needed to) 15g high with:
1 Dwarf Puffer
5 Ember Tetras
3 Oto cats
4 Endler's Livebearers (2 male, 2 female)
Normally, I'd have the otos in with my betta in my 5g, but since my Betta just passed on to that big rice paddy in the sky, I'll probably move them back.
In any case, the first sign that something was wrong was that one of the female gups died, so I figured it had either something to do with problems with pregnancy or being harassed by the males all the time. Then, a couple weeks later, I find the body of the other female on the floor of the tank with about half of her eaten away. Looking around the rest of the tank and doing a mouseketeer roll call, I couldn't find one of the male gups. 3 down, 1 to go.
Doing some more research, I found that it wasn't uncommon to separate those gups by sex so they could devote all their energy to swimming around and looking pretty (or bland, in the case of the females) instead of making little guppies. So, I figure I just won't buy any more females and problem solved.
Yesterday, my betta, Erik the Red, having died, I decided I'd do my weekly water change a couple days early. I changed out about 50% of the 15g's water and got everything nice and cleaned up. I put in a couple ghost shrimp from my LFS that I picked up for my puffer to nom since there wasn't a whole terribly lot in the way of snails left in that tank and he's kind of a snob about eating much else.
This morning, after I woke up, I decided to do another Mouseketeer roll call for the fishies and lo and behold, one of my otos is missing! Everything else is fine, my 5 tetras, my puffer, the 2 other otos, ghost shrimp and remaining guppie.
WTH? I mean, seriously? Where did waldo go? (Or should I say, into whose stomach?) I checked in, around, on, and under pretty much everything in the tank. Checked the filter to make sure he didn't pull a nemo on me (which would have been a pretty good trick since he was darned near 2" long). What's happening?