Clams spawn in response to lunar cycles and primarily in the months JUL-OCT. Simple stresses such as heat or salinity change will trigger spawns. And this is really nothing to worry about or do major water changes .
I have had several to spawn in a tank and its just food and a skimmer will go crazy like it does when the snails have a little get together at the waters surface every yr or so. If its just one doing what they there is nothing to worry about unless its a 5 gal tank and loaded up and not running carbon.. That would do you as well as a good skimmer.
Tweak your salinity and or mess with the water temperature and increase or decrease your lighting and they will spawn also it can be simply chemically induced ..This is what i did when i had a spawning system set up tank was built to look like a rat maze.. all the water with sperm and eggs had to pass over and around every clam in the system..(:
But with what you have going one its nothing to worry about at all. You will always find the chicken littles of the world around different boards. Oh my God look the sky is falling
No matter what the problem is or was Massive water changes I guess they work for salt makers LOL ???