Today, periodic mortality phenomena occur due to the use of well water (high iron content) in salmon breeding centers, which is a sign of a rust-colored layer on the surface of tanks or ponds. This phenomenon is due to the deposition of iron on the surface of the ponds and as a result the spread of iron oxidizing bacteria such as Ganionella, Leptothrix and Crenothrix SPP, which use ferro iron (Fe+2) as an energy source. The mentioned bacteria convert ferrous iron into ferric iron (Fe+3), which results in an orange-red color deposit on the gills and fins of the fish (Figure 1).
In the research conducted, it was found that one-year-old rainbow trout were exposed to Fe+3 iron with a concentration of 2 mg/liter for 2-3 days, and signs of iron deposition were observed on the gills of the fish. It should be kept in mind that lack of oxygen and acidic environment can lead to the increasing growth of iron oxidizing bacteria.