Derasa that's staying closed

[IslandCrow]

I'm wracking by brain on what's going on with my derasa. I've had it for around 7 months now. There's one other derasa in the tank that I've had for about a month longer. A day or two ago, I noticed a hermit crawling around on it, which is not unheard of. It looked like this one was just in transit trying to get to a tasty bit of algae. Of course, when it touched the mantle, the clam closed up. . .again not so strange an occurrence. An hour later, though, it was still closed. A day later. . .still closed. Granted, I'm at work all day, but I'm assuming it's closed at least most of the time then. I have noticed it open less than an inch with the mantle only barely extended past the upper margin. The color still looks good (i.e. no bleaching or browning). I also did a close inspection of the shell, and I don't see any evidence of damage or parasites. I do have a plethora of asterina starfish in the tank of late, and there were 3 or 4 of those crawling on the shell, but I can't imagine that would be an issue. Otherwise, I can't think of anything I've done differently to the tank. My alkalinity has been a little low of late (I think my tube on my peristaltic dosing pump needs to be replaced) and my calcium has been a little high (again, dosing pump issues). The only other thing I can think of trying is a freshwater dip. Any ideas? Oh yeah, here are the obligatory water parameters:

Temp: 78-80 (AC III/Heater/Chiller controlled)
Nitrate: 0
Nitrite: 0
Phosphate: 0
PH: 8.0-8.3 (or so I think, my PH probe is having issues. . .when it rains, it pours)
Alk: 2.5-3.0 meq/L (It's been dropping to around 2.5 or less during the day and I bump it up to 3.0)
Calcium: 500ppm
Salinity: 35ppt (SG: 1.026)

Tank is a 46g full reef (primarily SPS and LPS), 3 1/2 years old. Lighting is a Tek 4-bulb T-5. Bulbs are 7-8 months old. None of the corals are in physical contact with the clam.

 

[mc-cro]

what fish do you have. I had a Derasa and a hippo tang for years with no issues. then I noticed that my clam had been closed for several days, much like you describe. So after a few more days he still wasnt opening up like he had been. So I sat back in a chair on the other side of the room for while and just watched, sure enough, the hippo had developed a taste for clam.

 

[IslandCrow]

Sorry, I should have mentioned the fish. I have a maroon clownfish and a Smiths fanged blenny (Meiacanthus smithii). I've never seen any of them taking interest in the clam, and the clam really isn't in the clown's territory, so it's unlikely she's messing with it. I've had the clown for over 3 years and the blenny for about 2, so although these are the first clams in the tank, and anything's possible, I am pretty familiar with their overall behavior.

I'll be home all weekend, though, so I can keep a closer eye on them both.

 

[a4twenty]

did you inspect the new clam for pyramid snails before adding him??

if not check them both an hour or two after lights out.

try covering the clam with a clear pop bottle with some holes cut in for flow ( or similar ). if he starts to open, he is likely being picked at by one of your fish but i think those guys should be fine.

your Alk is low for that Ca and it doesn't appear to be stable which is very important for clams.

whats your Mg??

the best information to diagnose a clam is a couple of pics from above, we can tell a lot from them.

please post a couple of pics, of both clams.

 

[IslandCrow]

I did check for pyramid snails, both before I initially put him in the tank as well as when he stopped opening up. I didn't even think about covering him. . .of course, I also wasn't thinking about the possibility that he was getting picked at by a fish.

My calcium and alkalinity usually don't swing like they have been. My doser has just been acting strange over the past few weeks, and I'm slowly getting it dialed back in. At first I thought it was just an increase in demand, but. . .I'm working it. My magnesium is pretty stable between 1300-1350. My PH has been my bigger concern, but I'm 90% sure my probe is just going bad. I've actually seen it read as low as 7.5, which is obviously an error. It's always stayed between around 8.1-8.3, especially now that it's getting warmer and I have the windows open, so I truly doubt it's any different.

OK, all that said, I do have good news. I just got back home, and the clam is opened up and looking like nothing was wrong. I moved it from its normal spot yesterday evening, so it could have been that something in that area was bugging it. Clams don't seem to be too picky about water flow, so I'm pretty much ruling that out. I'll be testing my water later today to see if I've gotten my alkalinity back under control.

Here's some picture of the clam as a healthy clam. I didn't bother posting a picture, because it was just closed. There really wasn't much to see.

Yes, they're all the same clam. . .

 

[a4twenty]

good news, keep an eye on that Alk, it is very important to clams. the reason i asked about the Mg is that Ca, Alk pH and Mg are all related and if you're having rouble maintaining one it can be because another is out of line.

hopefully everything is working out ok

 

[IslandCrow]

Yeah, gotcha on the relationship between Ca, Alk & Mag. I checked out my peristaltic pump, and it was indeed dosing inconsistently, which is why my alk was off. I've replaced the tubing, so I should be back in business.

The clam's still looking good. I wish I could be sure exactly what happened, but whatever it was, hopefully it won't be an issue in the future. Thanks for all the help.