Derasa - Color Change

[Almondsaz]

I have had my Derasa for about 1 1/2 years and it has always seemed to be very healthy and forgiving of being my first clam. In the past two weeks I have noticed that on some of the edges the color in the margin is starting to fade to white and there is a white patch (almost square) under it's siphon. I feed once a week (reefroids) to put filter feed in the water column....so I am not sure what is happening. He gets plenty of MH lighting (150w) and is not in a shady place. None of the other parameters have really changed. All my water tests are in the normal range.

What health sign is this? Is he dying or going through a phase, or parasites?

Would appreciate any help and will post pics in just a couple of minutes - will take on as he appears today.

 

[Barry N.]

My first thoughs after looking at the picture, would be "bleaching".

The color of a clam comes from pigments in the zooxanthellae. Loss of the pigments. This can be caused by several things, increase in lighting or high temperature.

With that being said, this can also be caused by under lighting and lack of nutrients. If there isn't enough light to promote photosynthesis, the zoo will simply starve to death. Salinity too high or too low can also be a problem.

 

[Almondsaz]

Barry: thank you for the reply. My DT is on a chiller and there is nominal variation in temp. My salinity has always been 1.024-1.025 with the latter being 95% of the time. I have tried moving the clam up a little and if it isn't in the sand bed....it isn't happy and will close quickly to move itself off the rock and onto the sand. It just seems odd to me that everything has been 'stable' and then all of a sudden the clam starts to change. Should I try putting it on the rocks again? Is there a trick for success? Thanks again. David

 

[Barry N.]

Are you using tap water for top off? Best thing to do is think what you have changed later such as a different type of salt, new additives. If things were good prior the the change in the clam, then you might have to go back to where you were. But changes should be made slowly!!

Did you add a light bulb lately?

Keep an eye on it and it the bleaching get worse, then try to shade the clam a little at a time.

 

[Almondsaz]

I only use RO/DI water for top off and mixing salt. From day one I have only used Tropic Marin Pro and never had any issues. I have dosed magnesium for my acans - I have not dosed for a lest a week. I changed my bulbs about 3 months ago, so don't think at this point that is a contributor.

I will continue to keep a close on the Derasa and shade it should the situation not improve.

 

[Barry N.]

Here is a good example of bleaching.

 

[Almondsaz]

Barry: thank you, the photo is very helpful and looks like what is happening under the syphon.