Looks like suspended clay to me.
Is it a clay lined pond?

I would start with jar test and ag lime.

Last edited by Clay N' Pray; 06/22/18 06:43 AM.
Half acre 30 year old farm pond, Mebane NC. Aeration & feeder.
LMB, CC, SC, BG, HBC, two no account welfare carp and nine seasonal Tilapia that all the other fish are terrified of.