anyways.. Is it safe to run without ac fluid in your system?
Yes. It is used to prevent corrosion, but since aluminium and copper don't touch each other, it will take forever to build up corrosion. It also kills unwanted organisms if you have some in your system (most likely open systems).
And what kind of water do u have to use actualy ? (distilated or demineralized h2o ) ?
Demineralized. Actually destilled water is pretty expensive. If it weren't for the minerals in tap water, you could use that too.