Note that as 5-nitroimadazole compounds, both Dimetridazole and Metronidazole are photosensitive and more stable at acidic pH
(So keep the lights off, maybe add dark paper to tank back and sides if there is considerable ambient light, eg sunlight or bright room light illuminating tank; obviously you can brighten the tank for water changes etc)
Assuming your tap water is hard and alkaline (re pH 7.9), you might consider moving the male ram to a hospital tank and adding in RO water - do this gradually so as not to stress an already ill fish
Levamisol is also more effective in softer, more neutral water (IIRC suggested range is ~ pH 6 - pH 7.4)
(So keep the lights off, maybe add dark paper to tank back and sides if there is considerable ambient light, eg sunlight or bright room light illuminating tank; obviously you can brighten the tank for water changes etc)
Assuming your tap water is hard and alkaline (re pH 7.9), you might consider moving the male ram to a hospital tank and adding in RO water - do this gradually so as not to stress an already ill fish
Levamisol is also more effective in softer, more neutral water (IIRC suggested range is ~ pH 6 - pH 7.4)