if your corals are doing fine...normally, this is a good sign that a clam should do pretty decently as well.
post your parameters as well...just for information's sake.
mine are now: temp 78, mg 1350, alk 9.6, ca 430.
the clams i kept have been in the craziest conditions: very infrequent water changes (with old tank water from my 180g nonetheless), old halide bulbs from the 180g...sometimes without a bulb change for three years, large'ish temp swings, no calcium or alk supplementation for weeks on end etc etc. i am NOT recommending that anyone do this...i am just stating that clams can take a lot of craziness and still do great.
what i found to be important for clams is halide lighting (sorry about my biasness t5'ers

) and moderate to gentle water movement. my clams thrived in a skimmerless/infrequent water change tank for years with great growth...even with the poor alk/ca supplementation schedule.
now...i am a little 'worried' about my new office 90g *clam* system in which i transferred all my clams to. in the tank is good aged established live rock (marshall and tonga branch), gentle water flow and great lighting. what is 'different' on the system is the addition of a ca reactor that is now consistently keeping alk/ca levels where they 'should' be...whatever that 'should' is. if the clams start to show signs of stress because of consistent alk/ca levels, then the ca reactor goes offline. what were my parameters before? crazy would be the descriptive word. alk ranged from 6.5 to 8.0, ca was usually around 370, mg was 'probably' at 1150 and temps ranged from 74 to 82 depending on the time of year. in the summer it could be 76 to 82 in one day. in winter, it can range from 74 to 77 in one day. thus, even i am surprised that i havent lost a clam in years with this 'almost' negligent maintenance schedule.