I have lived in areas where the houses all had well water as a water source. Without a filter, almost all of them had very high levels of iron in the water as well, in fact most of the toilet bowls would be rust red inside after awhile.
I'd bet that high a level would not be too good for fish. Well water also absorbs alot of whatever is contained in runoff. Fertilizers, insecticides, etc.
Without a doubt you'd still need filtration, maybe even moreso with well water.