Sickness in the Tank

Question
Hello,  I have a fish tank with glo fish, zebra danios, neon tetra, plecostomus (sp?), and these strange silver fish my brother put in there that no one knows what are. (lol).  Right now I'm having a problem with my danio, zebra and modified alike.  I noticed it a week ago, the danio would start looking skinnier, and skinnier, until it's belly was hollow, and it would die.  It was only one at first, then two, and now I have two more ill.  I'm going to remove them and use clove oil and vodka to put them to sleep, but I want to know if my other fish are at risk.  The danio tend to prefer the top of my tank, the neons and the rest prefer the mid level or bottom, and I don't know what's causing this.  My brother and father and I all take care of the fish though I'm the primary owner, and sometimes I find strange treats or such next to the tank, so I don't know what may have been done to them.  Can you please let me know what's probably causing it, how to fix it, and such?  I'm hurting for my poor little fish, hollow bellies and starving to death can hardly be pleasant.

Answer
Hi Mary,
I am not the "expert" you asked because this question was sent to the pool.  However, I can try to give you some information about your situation.  Tuberculosis in a fish causes the fish to have a hollow belly, and become emaciated, which means "bony" thin, due to starvation.  And these symptoms match the symptoms you are describing to me about your fish.  There are no known treatments for TB in a fish.  Since I am a nursing student, I deal with hospitalized patients all the time.  TB in a hospital can be spread very very easily by airborne contact which leads me to believe that it is spreading throughout your tank as well by water.  What I suggest is to do many water changes to keep the water at top quality so the fish will have reduced stress.  Also add aquarium salt to reduce the stress of the fish.  Less stress will allow the fish to fight back against the disease.  Another thing you could do is do a 100% water change along with the aquarium salt.  Hope your fish make it.  Sorry I cant be of further help.
-Matt-