| Re: Antibiotics
If I haven't already said so, welcome to the forum TetrasRMe!
IME and based upon what I have read recently, it does appear that erythromycin is a good antibiotic which does not greatly affect beneficial bacteria (biological filtration). I can't say the same thing about minocyclin since I have no experience with it...but can say that, in order to reduce the risks of killing your biological filter with antibiotics, you would want to use one which targets gram-positive bacteria since the beneficial bacteria we need in our tanks is gram-negative.
However, you can do yourself a huge favor by using any antibiotic very sparingly in order to avoid a bacteria strain which is resistant/immune to these meds....which, IMHO, should be the case when adding any medication or chemical with very very few exceptions such as those chemicals which remove/neutralize chlorine. | 
