Black Mollies have protruding eyes and skin slime
Two of my girlfriend's Black Mollies have a big, protruding "pop eye". The other eye, however, looks perfectly normal. Also, both fish do not show any other disease symptoms. Only the bigger one of the two sick fish shortly stood directly beneath the water surface in a dark corner of the aquarium, shortly after he then behaved completely normal again. However, there is a light milk-colored 'seam' visible around the eye visible on this fish. I do not think it is a fungus, but rather increased slime secretion. Am I right here? I tend to think that these two fish are suffering from a bacterial infection that causes the eyes to protrude.
I think fungi are indeed very unlikely, as they look like cotton fluff or mold (which it actually is). In case of milky layers an infestation with bacteria or single celled parasites (Costia/Ichthyobodo; Chilodonella etc.) is likely. This takes place relatively frequently when Mollies from brackish water are kept in freshwater. Mollies are originally brackish water fish and can even be kept in saltwater! If you wish to keep them in pure freshwater (which of course is often the case, since Black Mollies are very popular for community aquariums) you should make sure you purchase animals from the above mentioned freshwater breeding strains.
How would you conduct a treatment of the ill fish?
sera baktopur is recommended as an immediate measure; sera baktopur direct is advisable if this does not lead to considerable improvement after 2 - 3 days. Support with sera ectopur is recommended. In the long term, all Mollies that do not originate from the above mentioned freshwater breeding strains should be kept in brackish water. A salt level of 0.5 % is OK, but the animals tolerate widely varying amounts. The fish need not necessarily be kept by themselves in a tank; you can also keep them together with other fish from brackish water.
Dr. Bodo Schnell