my guppies tails are losing their tails. within 12 hours they go from being perfectly normal with full tails to having only thin white strands left and then die. i have a photo but unsure how to upload. there were 3 neon tetras with them and they may have been nipping at their tails but i separated them and they guppies tail still just disintegrated within an hour. im not sure if its because if it had already been nipped at or fin rot. please help. thanks

I would do a good water change, about 30%, and then add 3 g of salt per L of water.

Dissolve the salt in hot water first then add it in 1/4s over today

Do you have any other fish in there (cats and the like) as some fish don't like salt

Do you know the water parameters?

Definitely sounds like fin rot - the advice Blueether has given is good.

If you see red streaks appearing in the tails then it has turned to a bacterial infection and you will very very likely need to go stronger than salt but salt and water changes should do it otherwise.

thank you. sadly my two remaining fish died over night. but i will add the salt and re-cycle my tank before i add more fish. my other tank with cichlids in it may be affected too as i had the guppies in there at one point and my cichlids tails look a lil warn. should i add salt to that tank too? i have already added stress coat.