I've got a 20L with two of the HOB refuges on the back. One of them doesn't have a light and is a couple inches of live sand and about 6 inches of LR rubble. The other has a Jali light on it and it grows cheato and pods to fast that I end up throwing the cheato away. The last time I got lazy with the cheato and I literally pulled a square "brick" of it out of the fuge. While they aren't as nice as a below the tank sump, I wouldn't label them as "snake oil" either. One fantastic benefit of them is that the pods have a gravity shot into the tank instead of running the impeller gauntlet of a return pump. While many pods I'm sure make it through a return pump, the gravity feed into a tank would be preferable to me, if I were a pod.
Eric
