Thanks for the previous help about six months ago with some questions on my 90 gallon reef. I am sure you do not remember me because I assume you have read tons of others emails since we last spoke. I was so pleased with your advice I plan on getting the hang on side refugium from CPR as you recommended. I also started adding magnesium like you advised for my crustaceans.
Anyways, to get to the point of this email, I was wondering if you could help me out with ID's on some strange inhabitants in my system. I have taken photos and left them in their larger size so that you might be able to zoom in and see them closer, though I have to admit, it wasn't easy getting them.
First, the 'Crab' was discovered in my sump tank just a few weeks ago. He hides a lot but once in a while I catch him hanging onto the filter sock at night, as I have captured in the photo. It has a very thin body and sort of looks like an emerald crab but has a brownish green body, striped front claws and very long feelers. I see him eating pods. I am puzzled because I have not added anything to the system for months. Is it dangerous? I'd say his overall size is no larger than that of the average thumbnail.
Next is the question that has me terrified. At night, there is on my glass tiny little spiral shell snails. They are milky in color and on the shell, which is also milky white, they have a hairline brown line and are no larger than the letter O in this text. They also have visible antennae in which reminds me of the single eye stalk of the Nassarius Snail. I read on Online forums about "Tiny snails" with no further descriptions in which others have warned will kill Tridacna Clams. I do have said clam and I fear for its health now with these critters. If these are indeed a threat, what is the best way to eradicate them? One thing further that I wanted to comment on is that my husband and I noticed a lot of these snails living in the algae, which is contained in my overflow chamber on the back of my tank that leads to the sump. I was told by employees of "That Fish Place" that as long as this algae was not affecting my display it would not be a problem and actually a natural beneficial phosphate filter. Do you think cleaning out my chamber is a good idea? I must admit I have been monitoring my parameters closely and since I have left this alga in the chamber the levels have dropped significantly.
The last question is also about a nighttime critter. I have noticed along with these little snails there are tiny white oval shaped "slug" looking things. They have no shell and remind me of a very ugly small Nudibranch. They almost look like a saltwater "Pill Bug" (or rolly-polly, or potato Bug depending on where you're from) but white and not gray. They just climb the glass and disappear by morning. Are these critters, if you are able to ID them, a threat to my system?
The animals I have are as follows:
Regal tang, Yellow tang, 2 Firefish gobies, 2 Royal Grammas, Tomato Clown, Mandarin fish, Watchman goby, Skunk cleaner, Tridacna Clam, 2 flame scallops, Blue tuxedo Urchin, Golden Zoanthid Polyps, Green Zoanthids, a Caribbean Mushroom, Purple mushrooms (not sure of genus but extremely hardy and splitting rapidly) and a Kenya Tree. Oh, can't forget the 2 Emerald crabs and Astraea snails and the little Blue Leg Hermits.
Goodness does everyone go through all these crazy creatures that come into the aquarium and just one day pop up to say hey we are all over!?
I really hope you are able to help me out again. Thanks in advance, and I hope you are having a well-rested and peaceful weekend.
Thanks for the letter and as for the photos, the crab is an easy one - get rid of it! I see anything with a 'claw' as a risk. Some are greater risks than others, but the one in the photo is just that, an unknown risk and I suggest disposing of it. While on the subject of crabs, the Emerald Crab is an intertidal species that when small eats algae, but as it grows, may also eat small sleeping fish and munch on some corals if not enough algae is available. I advise caution with this species.
As for the small white snails you have being a threat to your clams, I doubt that very much from what I see in the photo, as those that are dangerous to clams are cone shaped species that mainly stay attached to the clams foot area or outward side of the shell. At night it feeds on its juices through the mantle. You can see those snails on my website at saltcorner.com (Pyramidellidae sp.). Go there are compare to be sure, as your photo was not overly clear. Otherwise, those white blobs in the last two photos are just that - white blobs and not clear enough to make out anything. Maybe you can get a camera with a macro lens and get a sharper photo of them. To venture a guess, they may simply be Stomatella varia, often called the Shell-less snail, also shown on my website, even though it has what appears to be a shell-like coating sitting on top of its main body. If so, they are good scavengers and nothing to worry about.
As for the algae near the sump, the advice from That Fish Place is correct and would leave it as is.
Hope this helps,