Can you use distilled water with betta fish?

NO! Betta fish, like all other fish, use their gills to absorb oxygen out of the water that they live in. In doing so, however, they also absorb certain trace minerals and other nutrients that are in the water, much like we do when we drink it. Distilled water contains no trace minerals or nutrients; it is completely sterile, and therefore has a lesser capability of harboring oxygen molecules (the molecules have nothing to "cling" to), not to mention trace minerals and such. Humans should not drink distilled water because of its' utter lack of mutrients and electrolytes, so think of it this way: if you can't drink it, your fish probably can't live in it. He'll almost certianly die if you make him live in distilled water, especially if it's free-standing water and doesn't have a filter/water pump.

fresh water fish absorb water trough their bodies, the body acts as a filter that is where the trace elements are gathered from.the diet of the fish will make up for any trace elements not absorbed thouhg the water, betas have a breathing tube, from it they can get oxegen straight from the surface,they do not depend totally on gills for air, they can almost live in sewer water and survive " that's how they stay alive in thoes little jars they are sold in. distilled water does not hurt betas!