Hi,
If you don't know, currently I have about 3 Cherry Barbs and 3 Glowlight Tetras in my 15g tank.

The second day my tank was finished cycling, I bought two fish.

One GT and one CB. Then a week after that, I added 4 more fish (2 GT's, and 2 CB's) A day after the purchase, one GT died.

Then it was left to 2 GT's and 3 CB's.

(hope I'm not making you bored)
Then, another week after that, I bought 2 more GT's. The day after that, 1 GT died.
My problem is, everytime I buy new fish for my tank, they eventually die but only one from the purchase. I don't know what's wrong. I followed every procedure to put new fish but one fish eventually dies. Anyone out there, I need suggestions and advice. Thanks!
