When Fish Die..

[Aquaman187]

If you leave them in the tank it's like a white cotton that starts to develop what is that ?

 

[crunch7]

IMO That is white fungus, an infection which will not only contaminate the water but also act as a threat to other live fish.

 

[OldMan47]

Scoop them out. Whatever killed your fish is present in the fish but is not that white cottony fungus.

 

[Aquaman187]

No one died in my tank but I have seen it in other fish tanks before and was curious as to what it was.