Maracyn-2 which is Minocycline looses its effectivness at a Ph over 7 or in harder water. I'm not surprized it didn't do too much. For your water perameters Kanamycin is a better choice. While Furan 2 is also more effective in lower Ph or hardness in combination with Kanamycin it is very efective for this type of infection. Maracyn-2 is excelent in soft water low Ph SA or amazon type set ups where it would be the med of choice. This is one of the main reasons I ask for water perameters before suggesting antibiotics.