Help with refugium design/macroalgae selection


Active member
I am planning a 29 gal. clam tank, and plan to keep mainly just clams, a few soft corals, MAYBE a few SPS. Also, I plan on keeping a single male Lyretail Anthias.
I have heard that Anthias like to eat a lot of plankton??? and that you should provide an active refugium for them (as well as simply for the well-being of the tank).
My plan, (however lousy it may seem) is to plumb in a central overflow box that flows down into a 20 gal long tank as a refugium. This is really my only reservoir on the whole system, and it will simply contain a few baffles to separate the sand/algae from the main pump. Thus, the entire flow of system water (probably going to be around 400 gph) will be flowing through this 20 gal. refugium.
My questions are:
Is this do-able (with respect to flowrate, practicality?
What type of macroalgae would be suitable for this type of environment? (The refugium would have approx. 2" of aragonite sand and some LR, lit by two NO fluorescents)
Could/should I use caulerpa in this setting, seeing as how it is going to be a clam tank, and not primarily for growing coral?
One last thing, the refugium will have to be lit on a daytime period (same as main lights) because it is being kept in a bedroom with "light" sleepers :)
It is possible to have a single reservoir and not have to run all your flow through the refugium. Divide the 20 into two sections. Run the overflow from your main tank to the section with the pump but tee off a line to the refugium. Put a valve on the refugium line so that you can control its flow rate. The divider should be as high as you want the refugium deep. The water will flow through it at a rate you control and then overflow into the pump side of the reservoir.
I was actually thinking of something like this, but my only concern was for the drain. There will be 400 gph (possibly more) draining down a 1" pipe. I know that 90 degree turns and such slow the water when being pumped UP, but does this same thing happen in reverse?