by charlesr1958 » Thu Oct 15, 2009 10:23 pm
Yes, and no
Under normal or "good" conditions within an aquarium, the various bacterial species that are always present, such as those that consume dead organics are at a low enough population level that the fishes immune system can ward off any bacteria that try to consume the fish. But when a "dirty" tank, or one that has too many organics present, the bacterial populations explode and the fishes immune system can not deal with the massive amounts of bacteria and the bacteria are able to infect the fish. The gills and the eyes are usualy the first locations infected as they are the most "open" to the water, and hence, the bacteria. High organic levels are also a stress on the fish, which then lowers their immune system and with high bacterial levels, it becomes a double punch on the fish. So if a fish that is not infected and is in the same tank as a fish that is infected, it is not the infected fish that will pass along the infection, but the healthy fish could become victim to the high organic levels and to the bacteria just as the infected fish did.
Look at it this way, we humans are subjected to bacteria all of the time also, but immune systems fight them off and keep us from becoming infected, but if I put you into an enclosed room and pumped in extra bacteria and then didn't feed you for 3 days while your air supply became foul, I bet you have a good chance of catching an infection. Right?
Charles
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