Sounds like you have too many nutrients in the pond.
Spring is here and algae is growing. The biggest contributer
to nutrients in the pond is fish waste.
The foamy water is probably due to the frog spawn.

I would remove some fish and some of the frog spawn.
You can set up a kiddy pool with some of the algae growth
for the frog spawn in a shady spot in the yard.

k :-)