We let Cobra go today. We had him for almost a week and did all that we could. He went from possible swimming bladder, to fin rot.. to.. well I don't know. The fin rot was almost as if it developed overnight and rapidly. We just did a 100% water change with him last night and thought it would help.. It was hard for hubby and I. I am glad we were able to be there for him while we could. We miss you, Cobra!