Hey BettaBaby,

I do agree with Annie that your 10 gallon is very overstocked just with your goldfish alone, and is likely the cause of their troubles, and the previous deaths.

Do you test the water parameters (for ammonia, nitrIte, nitrAte)? I think if the params were taken right before a scheduled weekly waterchange, it would tell you a lot. Healthy water parameters would be 0 ammonia & nitrItes and less than 10 nitrAtes. The 10g may be able to handle the tetras...

What kind of goldies do you have? Are they fancies or comets? Even if they are small now... a comet can grow over 12"... and the fancies 6-8".... as well as the huge amounts of waste these maybe tiny goldies can produce. It is a hugely perpetuated myth that a goldfish should live in a goldfish bowl... so thinking they have a 10 gallon to share is not going to make it any better.

If your goldies are fancies... they are already predisposed to swimbladder issues, as Annie suggested. I'm afraid you're in for more heartache if some changes are not made for your goldies. They simply won't do very well in a tank that size.

Also remember to quarantine new fish for a minimum of 2 weeks but best to do 4-6. New fish can easily introduce pathogens into an otherwise healthy tank and wipe out all of your fish.

Good luck!

Michele