nitrate about 20 ppm (can't get it lower, doesn't really get any higher now though.
I just add some strotium and Iodine in small levels to keep some trace elements.
Will increase the mag a little.
The clam sits just off to the side of a 150watt metal halide, about 50cms of water between the clam and light.
Usually I give the tank water changes twice a week, thats about 25%.
Maybe the problems came awhile ago. and this is just the bulid up of a long time of not having the right conditions.
Thing is everything else in my tank is as happy as