im slowly building up my medications for the fish tank.i recently bought a bottle of protozin and when reading it,amongst others it is harmful for snails?can anyone tell me what the danger is? i only have 4 assassin snails in the tank to keep the pest snails down,what would be the routine for keeping the assassins if i had to medicate?and dont shoot me for saying this,but if it is a danger to snails,wouldnt it be an idea to use it to wipe out a snail infestation? not that i would....just curious.

Many meds are dangerous for invertebrates (shrimps etc as well as snails), and some fish are sensitive to the same chemicals that cause problems for inverts, usually copper in this case in the form of Malachite Green. Protozin also contains formaldehyde which is risky for certain scaleless fish.

Using meds unnecessarily because a side-effect is that they are toxic to nuisance tank inhabitants is a bad idea. You might just as well use a chemical snail killer (similar ingredients), which we wouldn't recommend due to the risk to fish.

In general chemicals of any kind are best avoided and meds only used when necessary and when a clear diagnosis has shown the most suitable med to use. Exposure to meds is always to some extent risky for all tank inhabitants, and using meds where there is no symptomatic illness may allow the pathogens it's meant to treat to develop resistance, causing problems further down the line. A bit like the way that humans insisting on anti-biotics for viral problems that can't be treated with them, or not finishing the course, has lead to the bacteria they can treat developing resistance.

EDIT: If you had to use a med that snails are sensitive to and needed to treat the whole tank, you would have to remove the snails during treatment.

as always,thanks for the info FL