Okay, sounds like they got toxed-out with hydrogen sulfide.
~ jan

What can i use for filtering that is fish safe and less itchy than
insulation?

Out of the pond filter? Or around the pump?

Around an in-pond pump I only have mesh baskets to keep the big particles
out till they break down to little particulars, then I made an upflow
out-of-the-pond filter like the flower pot filters show at the bottom page
of *My Filter* on my website www.jjspond.us . This can be stuffed with
window screening, or in my case, because I had extra open cell foam, I used
pieces of it and then three 1" rounds.

I filter my 1,000 gallon lilypond with a 19 gallon size pot, 700 gph mag
drive in-pond. 7 large fantail goldfish with a few goldfish and koi babies.
Lots of plants (and once I got the pH below 8.4) it has been perfectly
clear. ~ jan


~Power to the Porg, Flow On!~