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Ratpack
01/13/2016, 09:55 AM
This is the first Derasa that I have tried to keep. It looks different in my tank than it did at the store. There it was very open and full. It has been in my tank since Dec 21 and below is what it looks like now. It appears to be opening more lately, but I am concerned that the mantle is shrunk back as you can see in the photo. From what I understood, they do not require as much light as other species, so could the light be too much? I have it on the bottom off to the side. All SPS corals are great, but maybe it still needs more light. I have looked and do not see any pests on it, but maybe they are there. Please give me your thoughts on how it looks and anything I might try to make sure it survives.

http://i31.photobucket.com/albums/c355/ratfamily/Mobile%20Uploads/20160112_174239.jpg

SoloGarth
01/13/2016, 10:03 AM
Can you get a pic from the front? The inlet siphon looks to be "gaping" which is a bad sign.

If lighting is too intense the clam will bleach just like a coral. So that likely is not the problem.

Please post water params and equipment used for lighting and flow. Also how old is your tank?

JRR1285
01/13/2016, 10:30 AM
The most concerning thing I see in that pic is a shell that appears to have no new growth on it. There should always be a perfectly white area directly under the mantle at the edge of the shell. This clam looks like it has not formed any new shell in some time.

I would look at parameters such as Alk and Calcium despite your corals doing well they may have adapted to slightly depressed numbers over time. My tank fell into a period of low Alk and Calcium due to my neglect and some corals looked fine but the clam began retracting and gaping slightly. Raising Alk, Calcium, and Magnesium brought the clam around in a few days and it began growing new shell shortly after.

Since it has been in your tank receiving the same amount of light for a while maybe try moving it to a higher light area? Has the clam tried to move itself around at all?

Maybe also see if there are predatory snails or worms going after its byssal opening?

Be careful though, harassing and moving the clam in it's current state will not help things unless you are correcting a light or predatory problem.

Ratpack
01/13/2016, 11:14 AM
I will check the parameters to see if they have dipped, but a little over a week ago, the ALK was 8.5, cal was 440 and mag was around 1400. Tank has been up and running for about 7 years now. It has LED lighting. Last check had the PAR level where he is at around 110. He hasn't tried to move anywhere but the fish have knocked him over a time or two. He isn't attached in any way either, do they typically attach like the other species?

MondoBongo
01/13/2016, 12:15 PM
The most concerning thing I see in that pic is a shell that appears to have no new growth on it. There should always be a perfectly white area directly under the mantle at the edge of the shell. This clam looks like it has not formed any new shell in some time.

this is what i was thinking.

this is a clam that hasn't been healthy for quite a long time. he likely won't last a whole lot longer.

sorry for your loss.

T. derasa may attach when smaller, but as the grow their byssal opening shrinks and as adults they seem to rely on their weight alone to keep them in place. when i got my derasa it was little more than golf ball sized, and he attached himself to a medium sized chunk of rock. he's considerably larger now, and ditched the little rock a long time ago.

Ratpack
01/13/2016, 03:18 PM
Just checked parameters and Mag is 1440, Alk is 8.0 and Calcium is 380. So it appears something has started to uptake the calcium for it to drop 40 points in a week or so. My calcium is usually very stable as I dose each day with a doser.