White cotton wool and fish die off.

[Medesis]

New to the forum and in despair! Caught blanket weed from plants brought in from an aquatic supply company. Been really bad and tried everything to eradicate it but to no avail. More worryingly there seems to be associated with it what I can only describe as cotton wool type stuff which looks to me like a fungus (see attached). Now, I’ve had ponds on and off all my life and I’ve never seen anything like it. What is more I bought some grass carp the other day in an attempt to tackle the blanket weed and they died within 24 hours of me putting them in the pond and they had gotten areas of fungus all over their skin. They were beautiful healthy specimens when I put them in. I’ve got newts and frogs in there but they seem to be perfectly happy. I’ve checked all the usual water parameters and they seem to be okay. Do you think the two things are related? Any assistance would be gratefully received.
Cheers.

 

[WaterGardener]

Could you please post the results of your water tests? Thanks.

 

[j.w]

and welcome @Medesis
Could that be dead algae? If so maybe too much rotting and making your pond lose oxygen so fish can't breath. How big is your pond and how many fish did you or do you have at the time the fish died? I'd get a net and keep scooping out whatever that white stuff is and keep on doing it. Might have to run water in slowly and out to get rid of whatever is in your water. Test your water as @WaterGardener suggested.