Sorry I missed the question, Davey!
Unfortunately, T. maxima has the absolute highest mortality rate of all clams in the hobby. Worst being maximas under 3" and Color Teardrops.
In a nutshell:
Crocea require the most light, but are very hardy. The clams in the Hippopus genus are found at the same depths as crocea, but seem to be more tolerant for lower light and are very hardy. Great candidates for refugiums, as most don't consider them attractive enough for display. Maxima and squamosa are found at the same depths, and are similar in appearance, but the squamosa gets much larger. They are considered hardy, but babies and semi-adult/adult specimens do not adapt well to captivity. Same can be said for the gigas, which requires even less light, but a much bigger tank. The derasa is the best species for beginner clam keepers, as they require the least light, and are very hardy.
Gigas, derasa, and squamosa exhibit the fastest growth rates among clams, so a large tank with properly maintained alk and ca levels are a must, as these will get depleted quickly.
There's still a lot of unknowns regarding clam diseases and predation. Barry's done a lot in trying to identify the protozoan that causes pinched mantle, for example. Still, there's much that we don't know when it comes to internal maladies. A clam could appear healthy on the outside for months, but is actually on a downward spiral internally. Resulting in an unexplainable death.
HTH