Too lazy try and capture thier nests right now. I have four bettas and all of them seem to make nice bubble nests. I do the same as you and have an extra little tank and rotate my bettas with a clean tank about every 4 or 5 days. Anna taught me that little secret and it really works for me. I hate to change their tanks when they have a good bubble nest going. I'm always afraid that they won't build another one. So far they seem like happy little fish and always do. Blueberry and my blue/white one seem to build the biggest nests.

Max is very handsome!