What other parameters do you test for in your tank? What levels is everything sitting at? What's the temp and salinity? How deep is your tank? How far off the water is the light fixture?

My nitrates are 0 last time I tested. We usually buy the bottle of Kent with the clam on it but I currently have ChromaPlex. I don't have a sterilizer on my system.

You only test calcium and nitrates? Do you test for anything else? and again...temp and salinity? I'm not sure which bottle of Kent has the clam on it...can you take a peek at it, and tell us what it is?

Sorry Myka I must have missed your message while I was typing another.

The tank is 18" deep, light fixture is 4" from the water and the Clam is 4" from the water surface(moved from 8" yesterday).

Ammonia, Nitrates, Nitrites: 0
pH: 7.8
KH: 90
Ca: 480
Sal: 1.027 (making RO water right now)
Temp: 80F

I don't have the Kent bottle with the clam on it anymore but I beleive it was phytoplex.

I have a feeling it might actually be your nitrites, personally I run my nitrates at about 7-15 ppm and I have always had great coloration on them (including some fantastic color ups on clams I brought in later). Do you ever dose phylo or small particulate food?
Levi

How do you bring up your nitrates? I thought they were supposed to be low as possible.

How big is your clam? Per the literature, clams over approximately 2" rely mostly on photosynthesis to create their own food. At that size they get very little value out of phytoplankton and other micro-organisms. Yes, phyto etc. can offer your clam a boost, but its not doubtfully eating as much as you think.

Larger clams, again over ~2", do fine with a little bit of nitrates, or none at all. You are more likely to see issues with SPS when you have nitrates before you see it in your clams.

Croceas are just as hardy if not more so then any other clam in my experience. They adapt better, grow faster, and acclimate better then any other clam I've had, and I have had a lot of clams.

Your Tek fixture is just find for a crocea!

Do you have any additional photos of your clam. It honestly looks to me like it is is just further developing the colours in its mantle from the picture above.

However, given your description is sounds like part of the mantle is becoming spotty & transparent. Does this sound familiar? This is the result of zooanthelae either dying off or being expelled from the clam. You don't have to do anything in this case, its pretty normal and does occasionally occur from changes, like a move or a new system. The zooathelae will recolony and repopulate the tissue returning the colour to your clam.

One last thought; you and your LFS might have different lighting systems, thus making the clam appear differently in your tank then theirs. Same goes for depth and placement, etc.

If you want some fantastic reading take a look at:
http://reefkeeping.com/issues/subject/index.php

This is a link to reef centrals index for all of the articles written for there Reef keeping online Magazine. Some very informative stuff including this:
http://reefkeeping.com/issues/2005-06/rhf/index.php
A little bit of reading on Nitrate :biggrin:.
Nitrates naturally occur in your tank from the break down of organic compounds, now keep in mind if your have a SPS dominated tank then yes low nitrates are a great thing but for certain soft corals and clams some DOC/ nitrates are healthy. Take a look at Macro algae for example, macro algae feeds of nitrates/ phosphates in your water column. Harnesses the suns power and traps the bad stuff for you to remove it. Corals (and clams) contain a symbiotic type of dinoflagelleta which is used for there ability to photosynthesis. A very similar process happens here (keep in mind though its all about moderation, to much can be harmful). Clams being filter feeders also secrete a mucous to capture small things floating in the water (everything from detritus to coral spawn). That being said, having a water column with dissolved nitrate and small particulate to be filter fed should help the little guy color up.
Hope that helps!
Levi

Great link. Lots of good info there.

Your calcium and alkalinity is out of balance. Your alkalinity at 90 ppm is equivalent of 5 dKH. Proper ratios are:

1.4 dKH to 350 ppm
2.1 dKH to 375 ppm
5.6 dKH to 400 ppm
9.1 dKH to 425 ppm
12.6 dKH to 450 ppm
16.1 dKH to 475 ppm

The ratios need to be balanced for optimal absorbtion by corals, clams, and other life. Natural seawater contains 410 ppm calcium, and 7 dKH alkalinity. To convert dKH to ppm multiply it by 17.9. Keeping your alkalinity higher than it is now, and keeping it steady will also help to increase and stabilize your pH, which is on the low side for sure. It would be good to use an alkalinity buffer with pH buffering capacity like SeaChem Reef Buffer 8.3 in your case.

Although I doubt this out of balance is the cause of the clam's loss of color since you haven't had the clam in these conditions for very long, it may present an issue down the road if it is kept up like this.