I think mycobacteriosis took out all the rainbows in my tank over a month long period. I have read that the bacteria is very resistant to antibotics. What should I be doing to protect the other fish that were in the same tank?
You could start by reading my sticky on probiotic bacteria. Simple, cheap, and an effective method of competitive exclusion used within commercial aquaculture to keep pathogenic bacterial numbers to a minimum. Good luck.
will UV that simply kill non harmful bacteria in greater numbers than the mycobateriosis and thereby creating less competition,allowing more mycobateriosis, making the problem worse?
UV kills anything that passes through the light. Reduced bacteria/parasite count gives the fish a fighting chance. Your biological bacteria is on the filter media, tank walls, substrate are not affected.
Just as a UV sterilizer will not kill sessile/ beneficial bacteria, it will also not kill the Mycobacterium that are spread by direct contact, or other non- free floating means.
UV will only kill the bacteria that pass thru it, and that is if they have spent enough detention time under the UV to damage their inner workings. If the bacteria that pass thru the UV are sequestered within detritus, this can also lessen the UV effect.
UV is not a panacea
Some important facts in the article below. http://fisheries.tamu.edu/files/201...No.-4706-Mycobacterial-Infections-of-Fish.pdf
It's a very long thread, with a lot of info, but most of the US based members in that discussion are using Rid-X. But before you do anything, I suggest that you spend some time reading. That includes Duane's link as well. There is no magical easy fix, but you have some good info that will get you off to a good start.