I just noticed a oval shaped whitish colored worm about the size of the end of my small finger in our coral tank and possibly a second one which wasn't quite as large. It was eating algae on the back wall of our nanocube. I did a web seach, but I couldn't figure out what it is or if it may be harmful to our corals, although it seemed to gulping up algae and nowhere near our corals, but must be living in the sand, since there's no rock in that tank. Thanks!