You should actually do a few good sized changes with well aged/aerated SW
over the next week+. Once weekly will not be effective enough to help reverse the problem. The tank has a much higher nutrient level (DOC
) than before which is one of the more common causes of bacterial/Lympho problems. In milder cases the reduction in organics feeding the bacteria will often be enough providing the fish's immune system is up to par. Antibiotics are only needed where the problem persists or becomes enflamed/hemorrhaged.
Also be sure your foods are fortified/soaked with a good marine liquid vitamin high in [acronym="Highly Unsaturated Fatty Acid"]HUFA
[/acronym] prior to feedings.