My refugium is in the middle of my sump setup which is part of a 20L. I just have some chaeto/rock rubble/etc. I will try to get a picture of it later, not to much to see though. =)
Yes if you give them a place to hide such a pile of rubble. With that said though I'd recommend a refugium and a healthy ball of chaeto if you are wanting to supply enough to feed a dragonette or other pod eating machine such as seahorses.