You ever thought about trying goldfish

Even goldfish do better with regular water changes.

Holy doodles don't be so stubborn! You're getting some pretty sound advise. You don't need to take it word for word but to do nothing is a sure recipe for the clams to die.....

Suggestions would be welcome if someone knew what the issue was.
I was expecting someone to know why they're closed and then offer a solution.

Not offer 5 different solutions to be done at once.

So I'm going to do them one at a time and first I'm going to try and rule out a fish picking at it.

I just find it hard to believe that these clams are fine for 6+ months and then one day they just decide its no longer good enough at the same time. While nothing else in the tank is effected

Anyone who mistreats their pets buy not meeting the minimal standards to support life should not be keeping them

And yes clams are pets

The reason I chose a large tank with a large water volume is to eliminate drastic swings and water changes. Water conditions don't change at the snap of a finger. If the water conditions were deteriorating, it would be a gradual process and I would have noticed it.

Clams are not coral or fish

And who are you to say I am mistreating my pets and not providing minimal standards to support life? You know nothing about what I do with my tank and the extents I go to to maintain my tank.

OK Mark lets examine the plausibility of fish picking on them. First what fish do you have in the tank?

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