Antibiotics? Wont that kill off my good bacteria as well?
Some will, some won't. Generally, things like malachite green and methylene blue will kill off the filter bacteria (some of which are gram-negative) when higher doses are used, but most generic antimicrobials will not because they either do not contain those or contain low concentrations of them and also rely on other things to do the job.
For example, eSHa 2000 by eSHA labs is an antimicrobial medication which is marketed to treat aquarium fish against fungi (antifungal), bacteria (antibiotic) and parasites (antiparacitic). So while it is an antibiotic, and it kills both gram-negative and gram-positive bacteria, it does not kill *all* bacteria. In my personal experience with it, using a double dose of this medication will not affect the filter.
If you want to read more about what I wrote about cyanobacteria at one point, see http
/blog.natureaquarium.co.uk/?p=487 (and if you discover anything that I can add to that, let me know!)