Algae Eater Infections

Several of my fish have intestinal parasites and will soon be medicated. 
 Since many algae eaters eat more than just algae, does anyone know of 
intestinal parasite infestations in otocinclus and bushynose plecos?  I'm 
sure the Cory catfish and mystery snail are infected because they would 
consume eggs excreted from the contaminated fish that fall to the gravel. 
 And I'm debating about the Singapore shrimp.  Even though they are filter 
feeders, I have seen them working the gravel, too.  I am not happy about 
this at all.  :-(

The recommended medication is Metronidazole, Seachem brand, which can be 
both fed and dissolved in the water.  I called Seachem and the person said 
there was no effect on plants, but he didn't know about the fw snail and 
shrimp.  In saltwater, no invertebrate should be treated, but he believed 
freshwater invertebrates were "tougher."  Has anyone used this medication, 
either fed or dissolved, in their planted tanks?

I have a 125gal planted discus community tank.  The non-discus fish are not 
affected by the parasites (if they are even infected!) but discus are 
extremely susceptible.

Thanks for opinions!
Rochelle Williams
williaro at ftmcphsn-emh1_army.mil