will adding a sea shell to a freshwater fish tank kill a fish?

[Vin]

i put a big shell that ive had for a very long time into my new freshwater tank. i only have a small shark in the tank...i cleaned the shell off but when i put it in the tank, the outside started to decay kind of or the "residue" kinda loosened off of it. my shark is eating the residue...can this harm it?

 

[Bob S]

i dont think so, u should put it in the dishwasher before putting it in ur tank, a delicate wash.

 

[waAh]

most probably it won't harm the shark. if you put seawater though it would harm freshwater fish (they'll shrivel up )