:bounce: Because refugium can be so interesting/pretty people quite often place the refugium slightly above their main display tank. They pump water up to the refugium tank and let the overflow from the refugium drain by gravity back into main display tank. This requires a bulk head be put in refugium tank though. I have seen some very impressive refugium tanks over the years. Even seen them with sea horses. Refugium with gravity overflows into main display tanks supply good levels of natural foods to a main display tank in addition to be good denitrifiers if deep sand beds are included. A 29 gallon tank is good for refugiums with deep sand beds as they are tall tanks. As for refugium size in comparison to display tank size.,have never seen studies in relationship to size. As long as you have flows through your refugium that will allow for matching tank parameters, all sizes are acceptable. In general though with refugium as well as sumps people tend to go with the bigger the better plan. The main thing usually considered in relation to size is the space available, because the cost of everything else such, as return pump and overflow or bulkheads and plumbing is essentially the same cost regardless of tank size. There is a considerable difference in costs of deep sand beds between tank sizes, as aragonite sand is not cheap and adds up in pounds quickly with deep beds. Usually inoculating a refugium costs essentially the same regardless of size, within reason, anyway. :^:
