Injured fish?

Question
Thanks Chloe,

We have been changing the water (25%) weekly and at times there is a strong ammonia smell, but all of the test strips come back normal.  What else should we try?

Thank you!
-------------------------------------------
The text above is a follow-up to ...

-----Question-----
Hi Chloe,

We have a 75 gallon tank with 2 bala sharks (one about 5 in. and fairly aggressive, the other about 2.5, both are 1.5 yrs old), two dollar fish (both about 2 in., both are 1.5 yrs old) and a 6 in. pleco (about 6 mo. old).  This afternoon, after cleaning the weekly cleaning, my husband added one angelfish, two tiger barbs and two "kissing" fish.  

While viewing the new fish, I noticed that one of the dollarfish seemed to be missing its upper lip!  The wound doesn't appear to be fuzzy and is slightly more to one side.  There are no other signs of illness/injury that we can see.  We're not sure when the illness/injury occurred, but it looks pretty fresh (pink flesh at site of wound).

Since we weren't sure what it was, we isolated the fish in a 2.5 gallon tank with a little aquarium salt.  We're not sure if we should try anti-bacterial in the water as well or simply let it be to see what response we get.  

What would you suggest?

After catching it to put it in the other tank, the poor thing is pretty stressed out!

Thank you for any suggestions.

Cheri
-----Answer-----
Hi Cheri,
Your silver Dollar seems to have mouth rot. This is caused by a fungus or bacteria. It may also be caused by poor water quality. Check your water for ammonia, nitrite and nitrate. It is contagious so you have done the right thing by isolating the infected fish. Keep using the salt as this will help along with daily water changes of about 30%.

Good luck!
Chloe.

Answer
Hi Cheri,
Is your tank cycled? This will explain why your tank smells of ammonia. Also, are you syphoning the substrate for any uneaten food and waste? You need to do this thoroughly as this can cause bad water quality itself.
For now try doing daily water changes.

Regards,
Chloe.