A week ago I bought 3 goldfish, 2 gold and one black. 2 days later one gold one died, I replaced it and then the next night the black one died, so agan I replaced it and the third one died. Today I was left with 2 one gold and one black and I have just lost the gold one. I do not understand why this keeps happening as the water has been oxygenated and purified, there is an oxygen plant and stones in the bowl. I have ownedfish in the past that have lived for over 15 years and have never had this problem before. The initial 3 fish were bought from the same pet shop and those have all died. The 4th one I bought died today and I have One black one left who seems to be doing OK, but worried we lose him too. Please help with some advise as to what I can do.