http://edis.ifas.ufl.edu/FA033

So Jo Ann tried droncit (a name brand prazi) with her goldfish and either the low
concentrations only knocked the gyros and dacs (monogenians) down temporarily OR, at
higher concentrations it ripped the gills up. She tried this stuff for around 6
months and gave up because of its affect on gills. Her GF were in reasonably soft
water. Soft water is not very protective against chemicals and metals.

The link above discusses monogeneans and that "Morbidity and mortality epidemics in
cultured fish caused by excessive parasite loads are associated with crowding,
inadequate sanitation and deterioration of water quality. Although monogeneans are
commonly found on wild fish, they are rarely a direct cause of disease or death in
free-ranging populations."

PP is very safe when stock solutions are used and the reason it is recommended by
Floyd et al is that it is also effective against columnaris which is likely to be
present with a monogenean outbreak. OTOH, the peroxide dip effectively kills both
dacs and gyros and is incredibly cheap and safe for fish and humans.

so now I guess it is up to everyone to pick their poison. Ingrid