$25 is too expensive for a questionable crocea. At $25, we are still at or above dealer cost, depending on the clam. I would take him at $10, maybe $15 if I thought he would make it.
In general, unless you have a separate quarantine tank, do not buy questionable clams. Why endanger your current clams? Every clam purchase must be scrutinized carefully for health. Quarantining new arrivals is important - at least to me.
If you have balls of steel, and are completely confident that the clam's problem is from lack of light, ask the LFS how long the clam has been there. If the clam's been there a few weeks or months under NO light, you can save him. Place him in low light to partial shade in your tank, and over the course of a few weeks, move him to greater intensity every few days or so. The change must be very gradual.
Palmetto discussed something similar to this in a different thread and pretty much hit the nail on the head with respect to partially bleached mantles.
The 2 major reasons for bleached mantles are:
1) Lack of Light
2) Lack of Dissolved Organics, Nitrates/Phosphates
There are lesser reasons as well, but you don't want to get into those. :bigeyes:
