Nids actually have next to<em>no</em>defenses in space against any long range attacks. Their invasion style is just to throw an endless number of nids and enough will make it through incoming fire.<br/><br/>As for them incorporating it, I<em>think</em>they wouldn't be able to, but they probably could come up with a counter measure given repeated exposure.<br/><br/>Shooting streams would be the least of our concerns though, ripper swarms if able to assimilate it would become infinity more lethal, even more so since given the tyranids methods anything they touch that turns into glass would likely by imbued enough that either the hive mind could control them as golem like creatures or they would just join the rippers outright.<br/><br/>It would be like a worse case grey goo scenario, except the goo would actually be hostile and not just self expanding.