I agree with Mr.Bob if p.h. and alk are in range. Also what type of gypsum did you use?
When we gyp our trout ponds aeration is shut down completely for 3 days and only apply to 50% of pond Then next day treat other half. If alk is below 30ppm we use aglime first to drop the clay then go to the gypsum


Scott Trava
Catskill Pond
http://catskillpond.com
scott@catskillpond.com
Returning Catskill Waters To A Simpler Time
EST. 1923