What color refugium light is best?

Most refugium-specific lights contain predominately blue and red LED diodes that produce a visually violet or purple spectrum of light. This spectrum is popular in horticulture and provides the macroalgae with spectrum peaks at the exact wavelengths they need for optimal growth.

While side-by-side tests with full-spectrum daylights consistently reveal that the red/blue combo can achieve more robust growth, it's still not completely unheard of to use a white daylight lamp over your refugium. In fact, the white spectrum lights will work to support macroalgae and offers a better viewing experience if you're creating a display refugium. In this case, the key is full-spectrum which means it contains the necessary peaks for photosynthesis, and most any coral or plant-specific LED lights are going to work. 

How much light do I need for my refugium?

The easy rule here is to supply your refugium with just as much PAR as your supplying in your display tank.  That doesn't mean you have to use the same exact light fixture, just ensure you are providing equal intensity. Under normal circumstances, this will ensure that macroalgae growth can outcompete the nuisance algae for nutrients. If you don't supply enough PAR inside your refugium, you may find that macroalgae growth cannot keep up in terms of exporting sufficient nutrient levels which leaves those nutrients available for nuisance algae.  

Keep in mind that a refugium is often a smaller space relative to your display and the macroalgae is likely in much closer vicinity to the light itself. Consequently, achieving matching PAR levels is easier which is why you can often use a smaller light but still get the PAR you need to match your display. 

The best approach is to use a tunable LED light that has enough power to exceed your goals. This way you can fine-tune the growth rates in your refugium to meet your tank's needs, even in a heavy bioload situation. The more light you add, the more growth potential and the more nutrients you can export in the process.

When should the refugium light be ON, and for how long?

It is best to run a "reverse photoperiod" inside of your refugium which means lighting the refugium opposite of your display tank. When your display tank lights are ON, the refugium is dark and when the display lights go off, the refugium lights turn ON. By doing this, you help combat natural pH swings that occur by absorbing CO2 (via photosynthesis) around the clock. Most tank owners run the refugium all night long which means anywhere from 8 to 12 hours total. 

Do I need to tumble my chaetomorpha?

The short answer is NO, Chaetomorpha doesn't have to be "tumbled" in order to grow.  With that in mind, there are some major benefits to providing extra flow in your refugium and tumble the chaetomorpha.  

Tumbling chaeto will grow in a ball or cylinder shape and as it turns, all sides of that chaeto clump are exposed to the light source which ultimately means better growth. You won't experience a decaying mass of chaeto under a thriving mat on the surface. The tumbling motion will also help flush away detritus that tends to collect amongst the woven strands of chaeto and ensures the water doesn't channel through your refugium. 

Learn more with BRStv - Refugium Mistakes: The WRONG Wat To Set Up a Refugium