He died fast.

[Tom Trochlil]

Tried a 2 inch gold maxima clam under PC lighting. Had 300 watts of lighting and positioned the clam four inches below the water surface. Lived eighteen months and grew fist sized. Died in a little more than a week.:(

[Omar H]

Did you add anything new?
Were you supplementing (calcium)?
Why do you say it died in a little more than a week? Wasn't your first statement that it lived for 18 months and it grew to fist size?

Given your statement of 18 months and the growth, it does suggest that something changed and perhaps went unnoticed. What are your water parameters?

Could also be that it came to a point that it needed more light than just PC lighting, instead of dissolved nutrients (i.e. phytoplankton).

Omar

[Ti]

Since it grew, I don't it starved to death.
ditto, did anything change in your tank?
see any snails?

[Tom Trochlil]

The two parameters that people would point to that were out of whack were nitrate at 40 ppm and phosphate at 0.5 ppm. Both parameters have been like this since mid-October (I have been trying to reduce them but it apparently is a slow process).

Seems to me that if either of those water parameters caused it the clam would have given up the ghost months ago, but maybe it takes longer than I think.

Actually as I was looking back at the history of my four year old tank, I have had a number of items that fluorished for a year or more and then crashed (contrasting with some items that have been in the tank for four years).

Here's a list of things that grew rapidly for at least a year and then crashed.

Golden toadstool
Orange Montipora Capricornis
Kenya Tree

Like they say, good things happen slowly, bad things fast, in this hobby.