[richard5471]

Hi all!

Quick question for you. I have a small reef (24"x15"x15") and lighting it with 1 T5 white, 1 T5 actinic, T8 Powerglo and T8 actinic, all 22" tubes. Do you think there is too much actinic light and should I change the T5 actinic for another T5 white?

There is a mix of hard and soft corals by the way.

Many thanks in advance!

Rich

[Poseidon]

I think once a "proper" level of white light has been achieved, actinic is just for looks. So if you feel there is to much blue, then replace a blue bulb with a white one. If you like the looks of your lighting, leave it be.

[Ninong]

Hi richard5471, welcome to Reefland!

You could go either way with your lighting. Within reason, your corals will adapt to the available light. There are two factors to consider: Quantity and spectral quality. As far as quantity is concerned, a full spectrum fluorescent lamp has, on average, three times as much of it as an actinic fluorescent lamp. However, the actinic fluorescent lamp concentrates all of it's output in the important 420-450 nm range. This is important because the most common pigment, chlorophyll-a, has maximum absorption at 430-440 nm and again at 670 nm. So the actinic lamps are giving you extra energy in a very important part of the spectrum. Other pigments utilize other parts of the spectrum.

You are engaged in a balancing act that has to take into consideration the needs of the various corals and, to some extent, the aesthetic appearance of your aquarium. To provide examples based on the popular URI VHO fluorescent lamps, a combination of 2 AquaSuns, 1 ActinicWhite and 1 SuperActinic would provide the most appropriate light for SPS corals from shallow waters but it wouldn't be as pleasing aesthetically as 1 AquaSun, 1 ActinicWhite and 2 SuperActinics. And who wants to look at an aquarium that they think is unattractive? Furthermore, since most hobbyists who light their tanks without metal halides usually do not attempt to keep mostly SPS, they want a combination of lighting more suitable to a wide variety of corals. This leads us to the most widely employed combination: Two ActinicWhites and two SuperActinics. That's the 4-lamp compromise that seems to please the most people.

One combination that you might want to consider would be making both of the T5's white and both of the T8's actinic. When I say "white," I am talking about whatever they call their lamp that would be comparable to URI's ActinicWhite lamp -- which URI now says is 12,000K. If your T5 lamps have Kelvin ratings, look for a rating of either 10,000K or 12,000K. There are two reasons why I would want to try out such a combination: First, the T5's put out a lot of light, especially the full-spectrum lamps, and second, the T8 actinic lamps have an excellent appearance and "effect" on the corals.

You can always settle on what looks most pleasing to you and then choose your corals accordingly.