more clams dead

[Aquattro]

Jayson, I have to disagree somewhat. Yes, clams like some nitrogen in the water, but I don't believe adding it as a supplement is required. Although my Salifert kit shows no detectable nitrate (or ammonia, for that matter), there is both in the tank at all times. I can watch the nitrogen bubbles rising from my sandbed. This indicates that there is a constant supply of nitrate in my tank. If there is enough for my sandbed to convert to a gas, there is enough for my clams to assimilate.
My clams concur with this hypothesis simply by growing constantly. This would also coincide with the amount, or lack of, nitrate in their natural environment. Thoughts?