fish seem to sink

[dozer]

I have a large tank with a mixed variety of fish...One by one, they are dying, but before they do, they seem to lose their bouency....They struggle to swim and act like they've swallowed something heavy..I have lost some danios and some cherry barbs so far.... My tiger barbs, gold barbs and brilliant rasboras seem to be OK so far...I know I lost a female cherry barb a few days ago (never found her...tigers take care of that) and I am watching a male cherry barb struggle to swim as I type this....This is obviously some kind of disease, but is there something I can do? I'm not big into adding medication to the tank, but will adding aquarium salt or Epsom salts help? The tank has been set up for years, and this started about a month ago..I do weekly water changes as I find that works for me to keep the pH steady....I have a huge live plant in there...I run an aqua clear water filter.

 

[Zagz]

First some more information, Tank size, tank occupants, water parameters exact numbers for ammonia, nitrite, nitrate and ph, how much water change each time, what do you feed and is anything new to the tank? Is there any other physical ailments?

You can add epsom salts to the tank but no guarantees it will help. Are the fish bloated at all?