The Hidden Claw Returns

I grew up in a house full of fish tanks filled with an extensive variety of fresh water fish, including piranhas. The first time I got fish of my own was for our pond, and we soon had a dozen or so carp and koi gracefully darting about the pond water. Although it's always nice to have gardening buddies (and fish are very attentive to what is going on in their backyard), they are reclusive and keep their private life private. I was very excited then when Simon bought me a reef tank a while ago: finally I would get to see right into an underground world filled not primarily (or at all) with fish. After procrastinating (salt tanks really are intimidating) for a very long time, I finally got serious and set it up early last Spring. A lot of thought needs to go into placing a tank as you sure as hell don't want to move it once it is situated. It can't be in the sun, can't be too cold or too hot. It needs to be by an electrical outlet and in a place that will neither get traumatized by too much activity but also not neglected. I decided the best place was my office at work. (It really is a good place and makes going to work a lot more interesting, knowing my Little Guys are there waiting for me.) The only expert on reef tanks I know is my nephew Stevie T (check out his extensive salt tank business), and he recommended moving very, very slowly. To give but one example, common advice is to spend 5 months (!) circulating salt water in your tank before you even add sand. So, I added water, waited. Then, I added sand and waited. Then I added live rock and waited a really long time. Then I added "reef cleaners" (more about that below) and waited. You get the idea. The really interesting (and alarming) part was after putting a "live rock" (the rock isn't alive, obviously, but it is coated with microscopic living things that will burst into reproductive activity once placed in salt water--think of a live rock as the functional equivalent of yeast in a bread dough) in the water and then a few days later finding the tank stocked with hundreds of various life forms: algae of all colors, sponges, various little insect-like critters racing about, sand worms, barnacles, anemones, and dozens of other things I can't even find information about. To try to get this sudden explosion of life under control, I then stocked up the tank with "reef cleaners," which are various creatures who clean tanks. I got about a half dozen of various kinds of snails, a few hermit crabs (who seem to spend all their time playing musical chairs with their shells) and a large and very shy arrow crab who spends all HIS (or her, I don't know, really) time collecting the empty shells and dragging them off to his hidey hole, which is a cave under the large rock pieces. Every time I go in the shells have been moved around. (Inspired by SpongeBob Square Pants, I call that guy Mr. Krabs as he is the boss of the tank.) The beauty of reef cleaners is that they eat garbage, skuttle about all day and night perfectly happy with their little hobbies, and leave each other alone so I never have to worry about territory disputes. One day, a few months ago, I was watching my crabs do their business when I saw a rather large maroon claw reach out from a little cave, grab at some detritus floating by and then--after we made eye contact--race back into his cave. This alarmed me because (a) I didn't buy this thing and (b) I didn't know what kind of crab this was and most crabs are NOT reef friendly. There is a reason crabs have very, very large claws and are (for their size) ridiculously strong. If this was an aggressive sort, my other little guys were in serious danger. The other part about crabs is that, despite having eyes the size of a pinhead, their vision is far better than mine and so if it came to me having to catch this thing to save the others, I didn't fancy my chance of outmaneuvering him. The internet was no help: I could find no pictures of anything that looked just like him and viewpoints held by various reef tank hobbiests were sharply divided: those that hate all crabs and spend enormous energy describing in detail how they kill any "hitch hiking crabs" they find in their tanks and those that love all crabs more than their own children and pepper their conversations with pictures of their crabs wearing outfits. One had a family of crabs all dressed like Lord of the Rings characters. So, I decided to play the wait and see game. Every time I went in, I would catch him waving a claw around outside his cave entrance and then, once he saw me, he would skuttle quickly into his cave, out of sight. (Also inspired by SpongeBob, I call him Krabby Patty.) Finally, about a month ago, I didn't see him anymore. At first I figured he could be molting and didn't dare leave his cave. But as the weeks wore on and I didn't see him, I figured he must have died. Then, today I saw a familiar sight:

I still haven't seen his whole body and so have no idea how big (or not) he is. And I'm no closer to knowing what he is. Or what he eats. Or how big he will get end up getting.