SPS Tissue

[JimD]

A picture would help, it may not be RTN at all, it could be one of several things.. Adding vinegar will dramaticly affect your Ph, not so much your Alk. If you want to lower Alk, discontinue the addition of the Alk part of the B-Ionic and only add the Ca. and continue with regular water changes untill its in range, I like to keep mine around 8 Dkh. If its RTN, it can and will pread to other near by corals. Best to do is to segregate the effected coral and place into a Q. tank. Gonna need a good pic first..