[Delphinus]

I've heard of people adding synthetic nitrates (sodium nitrate or whatever, probably the same thing used for fertilizing planted FW??) to maintain a consistent level of nitrate of 5 for the sake of their tridacnid collection.

So you're not alone in your thinking, although at the time I thought the fella was nuts, and to an extent I'm still not sure what I think about it. I have a 115g now with 12 clams and there is low nitrates but I don't think it's zero and I don't really think the clams are having a huge significant impact on the nitrate. I'm not sure, maybe they are. It's hard to gauge it objectively. I had a nitrate probe for measuring subtle changes in NO3 levels (because if there's one thing I obsess over, it's nitrate and phosphate levels), but the probe is shot and it's $200 to replace the probe (the whole thing costs around $250 in the first place so I haven't quite gotten around to doing that).

Adding nitrates does seem to go against intuition for reefkeeping but if you can demonstratively observe nitrates disappearing at increased rates then indeed I can see there being benefit.

The question I have though is, what would we think the benefit to be? Bigger brighter clams or just healthier longer living clams? Or perhaps higher surviving numbers when rearing juvenile clams (since the survival rate for tiny clams is, at least has been in my experience, not great).