What is happening here?

[inverted]

So I've moved on my stenomelania sp. to a new owner and she just contacted me said one of the snails is releasing lots of white particles in the tank.... Could this be a spawn? See the attached image. There is a video but not sure how to upload. If it is a spawn what should be done next?

[NoGi]

Can't you attach the video here? Otherwise, upload to youtube to the SKF channel and put the link here.

[fishmosy]

Certainly looks like a spawn. Gastropods (Snails) will release their gametes if highly stressed.

What led to this happening? Was the snail exposed to high temperatures?

Unfortunately it is unlikely the gametes/larvae will survive (even if fertilised) because they will require microalgae and (most likely)brackish water to develop.