Algae and hermit crabs

Part of the fascination and education with a mixed reef system is the behavior of the plants and animals.

This system is basically a planted saltwater tank at an early stage.  A large piece of Red Dragon in the background.  In general, we don’t “fight” so-called nuisance algae and have plenty of green hair and filamentous growing.

After adding about a dozen hermit crabs to one spot on the bottom of the display tank, they quickly spread out in all directions munching away.  After about a day, 7 or so of the bunch were tightly grouped on the very top of the highest rock mowing down green algae.

How and why did they all find the same small area?  There are many rocks and plenty of algae.  Can they hear each other, or “talk” to each other?

In any event, you can see from the white area in the picture (a poor iphone pic under white/blue LEDs) that they clean what appears to be 99%+ as they go. The purple areas are encrusting coralline algae that we want.

Very nice work!  Now we just need to vacuum the hermit crab dung which is much easier than removing the algae mechanically.

The hermits were purchased from an LFS (local fish store) for <$1.00 each.