I always liked the idea that Aliens possess multiple ways to feed and sustain themselves. To me they are living batteries - their acid blood is battery fluid and they need to be recharged. One way to do this is to hibernate next to a source that emits heat, radiation, static etc. For growth they obviously need nothing to grow, as the movies suggest. And if they are related to the Neomorphs, then it's confirmed - they just grow... It could be that that there is some hibernation osmosis involved here as well where they absorb or reconstruct matter for their bodies to feed on, or maybe it's just a way to grow chitinous armor. It could also be that when they hibernate the dorsal tubes both absorb matter and nutrients as well as spreading cystic spores that turn into hive growth. That could explain why the Runner arguable ate its victims and never seemed to start constructing its own hive - it had no dorsal tubes. Also, they're silicon-based lifeforms, so the idea that they can feed on non-organic materials to grow and sustain themselves isn't that outlandish, right?
