as stated your light is more than sufficient for any spieces of clam....as far as placement....derasas and squams in the sand and croceas and maximas on a small, flat or slightly cupped piece of LR that you can easily move and fit into your rock work (so you dont have to cut the clam off the rock if you need to move it).......also kinda puzzled by the ammonia reading......can you take a sample to the LFS and have them double check?......whats your Mg at?

My ammonia test kit was off, should be reading 0. I picked up one of thos squamosas today Ken, thanks!