What are some symptoms and signs of internal bacterial infection in fish?
 

thank you.

Bloating, lethargy, disorientation, lack of balance, red streaking in the fins and body are the primary symptoms. Anything in particular making you ask, or just looking for information for the future?

Just looking for future info :-)
What is internal bacterial infection usually treated with?

If the fish is eating, than feeding foods soaked in antibiotics is the best way. However if the fish is not eating, you need to find antibiotics that are not only water soluable, but tissue soluable as well. The most commonly available antibiotics that fit that description are Nitrofuran, Maracyn 2 (Minicycline) and Kanacyn.