a large refugium, while not necessary for success, is definitely a benefit if you have the space. increased water volume aids in parameter stability.
here is a pic of my 'modified' refugium on my 180g with a 100g sump. most of the times, people talk about their 100g sumps but in reality, they normally dont hold 100g unless one fills it to the top. but with this, then you dont have the sump being able to hold the excess water from the display when the main return pump is off for whatever reason. my total 'adjusted' volume estimate when i take live rock into account is about 250g for the display, sump and fuge.
the blue barrel is filled to the top with live rock. the white bucket is where i concentrate chaeto macro growth in one particular are of the refugium to maximize growth and contain the macro for easy harvest.
the light is a 65 w 6500 lights of america on for 18 hours a day. the bucket receives about 600gph (120x turnover) excess bleed off water from my pressure rated pump that drives the bermuda skimmer. the bucket input is via a 1/2" 90 degree elbow pointed at 45 degrees to get a rotational swirling action that spins the chaeto into a ball (which is the desired shape for chaeto) for maximium light exposure over the entire chaeto ball.
the bucket then drains back into the sump via a 1 1/2" pvc flex near the input of the return pump to pump any pods released by my refugium into the main display.
the live rock is for sponge and tunicate growth which, in theory, will help absorb stray silicates in the water. probably just a dream but it doesnt hurt to try. the bottom of the barrel has a ball valve to occasionally drain the bottom if it starts to gross up. it is also predator free so pods are allowed to grow and grow and grow!!!
barrel 'circulation' is achieved by having the white bucket drain deep to the bottom of the barrel with the pvc pipe going down near the bottom. additional circulation is with a coralife sl-38 airpump to pump air to the bottom and have the rising air bring deep water with it. this way, fluidized (reverse) flow is achieved. the air is great as well as the bubbles always create a random percolation which should decrease any dead spots.
video of spinning chaeto:
