New Reefer
am pretty new to all of this and recently spotted two new friends (?) in my tank. This is my first post on Reefs and I am going to try to post a couple of pics.
The first is coral or anemone and doesn't worry me much. He is quite small (6mm across) and will extend or withdraw his tentacles according to food availability in the column (he extends arms when I squirt a drop of Oyster Feast or other food into the tank). He will withdraw if a crab or starfish disturbs him.

The second has caused me some concern since reading about mantis shrimp on this site. I first spotted this little guy in a 'micro-cave' created where an old snail shell was leaning against the front glass of my tank. The shell formed a 'roof' and there was a small void underneath the shell. I spend a fair amount of time watching my tank through a magnifying glass ( I really enjoy the various 'pods that thrive in the glass/water/substrate junction). Anyway, this tiny cave is where I first saw movement and watched long enough to see this guy, along with another of the same size (and about 6 much smaller specimens) moving about and even moving bits of gravel as if enlarging their home. I caught one of them last night and the second one this evening by siphoning up the gravel around and under the snail shell 'cave'. The picture is not very good but I will try to describe what I can.
a- if he is stretched out, he is about 10mm in overall length,
b- antenna on the front of his head (like a lobster),
c- gills and 'legs' under the abdomen (like a shrimp),
d- two arms held in a 'mantis-like' pose (claws are not clearly visible - arms almost appear to have 'clubs'),
e- swims in a forward direction when hit with light or when trying to escape,
f- holds the tail in a 'curled' position except when moving quickly - stretches out completey when 'swimming' or 'escaping', BTW - they are QUICK,
Now, if these two 10mm critters (and their little brothers) are mantis shrimp, does their presence mean that I have a breeding population of adult MS in my tank? I have never seen a large stranger in my tank but have heard some 'clicking' which I attributed to a yellow tang that sometimes rushes around smacking his tailagainst the glass.
Thanks for such an awesome web site and any feedback will be appreciated.


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Advanced Reefer
The "shrimp" is an amphipod, I think. They're peaceful and don't get bigger than the one you caught.

I don't know what the other one is. A coral of some kind.


New Reefer
Thanks Brian. I will rest a little easier. I had no idea that 'pods' could get that big. I always imagined them as 'micro' bugs.


Experienced Reefer
The type of crustacean is commonly called a scud. Amphipod, (gammarus) What I like about them is
that they rarely get up and walk on their legs like a "dog" or whatever, but they lay on their
sides and use their legs to move when on the sand. Weirdest behavior. As for reef plankton
they are my favorite, mostly cause they are easily observed and kind of cool. They end up
everywhere, really digging on canister filters and skimmer bodies and such. No harm at all
and in fact they are really good to feed when your fish know it is feeding time, to drop one
of those into the water column and watch the action. Whenever I would clean out my Fluval
can filter, I could usually get ahold of about a dozen nice fat ones. Then I would feed the fish.


1. Amphipod of some sort.

2. Pseudocorynactis of some sort , a.k.a. Hidden Cup Coral - found worldwide in tropical and some temperate seas. Harmless other than possibly stinging other corals that get too close.

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