Yeah clams typically spawn when something changes in the water chemistry, they think something has changed for the worst and spawning is their attempt of spreading their seed one last time to keep the species alive. Once things stabilize they should settle down, hopefully. Just be glad they are not that big. All the clams in my last tank spawned at the same time, now that was a mess.

One was a fair size, I couldn't see in the tank for a day. The temp jumped up 5 degrees once I shut my basement sump down, which I wasn't expecting. But now I'm sort of rushed to get the fish moved over to the 180..

What's a fair size? One of mine was over a foot.