Is this fin and tail rot?

Question

We had two fantail goldfish that have been fine for around 3 months. We went and brought 2 more fantails on saturday and introduced them into the tank. The next morning my husband discovers my two old fishes tails and fins and in shreds. I have been watching continuosly to see if i have an aggresive new fish but have not seen any aggresive behaviour. Do you think they have tail rot or have been attacked? Also what can i do to help their tails will they grow back? One of them looks like i can see its tail bones :-(
I did look today and it seems more fluffier looking so i dont know if its new tail growing or like a fungus what a mess :-(
i just want my babies to survive

Answer 1

You should never add new fish without quarantining them for at least a month to make sure they don't add some kind of disease. Also depending on the size of your tank ,the 2 fish could of thrown off your cycle and caused stress, which lowers the immune system and makes them catch things easier. Goldfish need a minimum of 10 gallons each ,so unless your tank is 40 gallons it will be very hard to keep the cycle steady and safe for the fish.

Test your water and make sure you have zero ammonia and nitrite and at least 10 nitrate but not more then 20 or you will have to do water changes to get the params right. As long as the water is unsafe you wont be able to get the fish healthy. Once the water is safe though you can add something like melafix to help aid the healing of the fins.

Answer 2

I don't believe tail and fin rot can happen that severely overnight. In cases of rot, it will start along the edges of the fins and slowly eat its way inwards. The edges of the fins will lose color and turn gray, and will spread somewhat evenly over the fin, towards the base. It is most likely damage, but damage will cause fin and tail rot if not treated quickly.

Answer 3

it does sound a little to soon to happen but there is a possibility it could be both