Parasitic Or Bacterial

[evildead]

Is there a way to tell if a fish is sick from parasitic or bacterial internal infection ? I've had fish that was infected internally by either bacteria or parasite, but can't tell from the outside which it is and it's hard to remedy the problem quickly without knowing the problem. They don't want to eat and stay by themselves in a corner or alone. Sometimes they kinda try to want to eat but end up not being able to swallow it. Eventually if they don't get cured quick enough, their heart starts to become weak and their breathing becomes harder and die from weakness.

I can handle external problems easy but internal problems, can't tell.

If anyone knows how to figure out whether a fish has one or the other, please comment.

Thx