[Puzzdre]

just a few more words on
Erythromycin: Pharmacology


'Erythromycin can be considered the prototype of macrolide antibiotics. These drugs inhibit the ribosomal protein synthesis in bacteria and thus have a bacteriostatic and bactericidal effect. Erythromycin has a similar action spectrum as penicillin and includes in particular many Gram-positive bacteria; staphylococci are often resistant. Among the Gram-negative agents Bordetella pertussis and Legionella pneumophila deserve to be mentioned especially. Like the tetracyclines, erythromycin is also active against bacteria-like organisms (Chlamydia trachomatis, Mycoplasma pneumoniae, Ureaplasma urealyticum). '


so, it can kill bacteria but I'm not sure for algae...

second, one site said for Erythromycin: 'The base is white to off-white crystals or powder slightly soluble in water, soluble in alcohol, in chloroform, and in ether.'

as I see it, one can use any antibiotic handy and put it into the wc system to kill bacteria. Still not sure about the algae.