So I recently added a Panther Crab to my aquarium. All seemed fine. He dug himself a little cave among my driftwood, scavenged and foraged at night, ate the occasional vegetable I'd sink to the bottom.

More recently, I've been trying to add some Thai Flying Foxes to control the algae that wants so badly to grow on my plants. They worked fantastically for controlling that, until they began to disappear, about one per week.

I just a did a little experiment tonight. I turned out my aquarium lights and left the room light on, just to observe how my fish were behaving (I suspected another one of my larger fish were making a meal of them, but they generally seem uninterested in the flying foxes during the day). Lo and behold, my panther crab came out of hiding, foraged for a bit, then found a good hiding spot to watch the scenery. Every time one of my flying foxes would carelessly swim too close by, he'd try to snatch them up.

So what I'm getting at, is I think these guys are more than just scavengers. Can anyone confirm if they're actively predatory, or if my crab was just being defensive? Finding information on them is downright near impossible.