What Is The Best Refugium Light?

A refugium light does not need to be fancy or expensive. I get very good results and excellent chaetomorpha growth in my ‘fuge using just a single light bulb mounted with a spring-clamp bulb-holder.

The Best Refugium Light For Chaetomorpha Growth | Spectrum and Wattage

First of all, let me say that I’m a huge fan of chaetomorpha.

It is easy to grow, eagerly soaks up nitrates, requires very basic lighting and forms a thick growth that becomes a breeding ground for copepods and other planktonic organisms that are a food source for my corals and fish. My Mandarin dragonet, that has been with me for about 4 years already, no doubt benefits from the copepods growing in the lush chaetomorpha that find their way back into the main tank.

When I decided to turn a section of my sump into a refugium, I went out and bought a 2 x 24w T5 aquarium light fixture. I used two T5 bulbs in the 14,000K spectrum, and lo and behold, I got horrible chaeto growth!

I’m not sure if it was the 14,000K light spectrum, or whether the 48w of T5 lighting just wasn’t sufficient for the chaetomorpha to grow. I decided to pull the plug on the T5 fixture after a month. The ball of chaeto was getting smaller and dying back, turning white in some areas — a clear sign that the chaeto wasn’t getting enough light, in the spectrum it needed. Left as is, it would have soon died off completely.

I could probably have gotten good chaeto growth with four 24w bulbs but I decided against getting another T5 fixture to complement the first one. Surely there was a more cost-effective solution.

I mentioned my experience with T5 lighting and poor chaetomorpha growth to a reefkeeping buddy of mine and he seemed pretty confident that a single 60w lightbulb would be good enough as a refugium light. He himself was running an algae turf scrubber with great success using a plain old 60w lightbulb and recommended that I give it a try.

He also advised me to get a bulb in the 6500k spectrum — more yellow than the 14,000k’s and better for photosynthesis and macroalgae growth!

My Recommended Refugium Light and Reverse-Lighting Schedule Timing

I headed down to my local supermarket and after looking at about a dozen different lamps, I picked up an Osram 865/E27 11w light bulb.

This 6500k ‘cool daylight’ energy saving bulb takes up only 11w of power, but is rated at 55w. And best of all, it was cheap. A mere fraction of the price of what the two 24w T5 bulbs cost me. Oh well, I’ll find another use for that 24w T5 fixture somewhere down the road.

I mounted the bulb with a spring-clamp loaded light bulb socket and reflector that clamps right to the outside glass of my sump. I also put the light on a timer and set it to a reverse lighting schedule from the main lights in my tank.

I set my timer so that the refugium light comes on at 1130pm, a half hour before the main lights go off in my main tank at midnight. At 1030am, a half hour after the main lights come on in my tank, the timer is set to turn off the refugium light.

This reverse lighting schedule helps to stabilize pH at night. Most saltwater aquariums are notorious for dips in pH after lights out, sometimes dropping as low as 7.7 or 7.8. And as mentioned on our pH and alkalinity page, pH swings are not good for our aquarium livestock, especially our corals.

Indeed, even when I was using my T5 light fixture on a reverse lighting schedule in my sump (and despite the poor chaeto growth), the pH in my tank never fluctuated, remaining at a steady 8.2 to 8.25 throughout the day and night, as measured by my pH Pinpoint monitor.

Chaeto Growth At Last!

Within a couple of weeks of adding the new bulb, the chaeto had turned a lush, deep green.

And in a month, noticeable growth was already apparent. In fact, it had almost doubled in size.

Chaetomorpha needs good water flow, but rather than adding an additional powerhead, I place the return from my aquarium chiller into the refugium compartment of my sump. This way, the chaeto gets a healthy stream of flow from the chiller’s return. It is always interesting to watch the chaetomorpha tumble around from the flow — that is, until it forms a thick, green brick that has to be pruned back because of all that wonderful PAR it is receiving from a simple refugium light!

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