Mirrors in sump

All of it absorbs some of it. Otherwise glass would be completely invisible to us.

 

and thus you proved your first post wrong, thanks

 

Not really. Mirrors are a reflective coating on glass. The reason why they are so reflective is because of how smooth glass is, not because glass is transparent. In general, the smoother a surface is, the more reflective it becomes.

 

I think I got this thread off topic a bit, and for that I'm sorry to the OP. To clear the air, the quesition was wether or not it was safe to put a mirror directly into the water, and to that it's best to say no way hose`. I have seen cheap mirrors get wet just from typical water damage and the reflective paint material behind the glass does come off, and most likely wont be welcome in your reef system, or any other system at that. Best to stick with standard glass for seperators in your sump, or plexi glass.