Actinic light for plants

[Sea-agg09]

I'm considering purchasing a compact flourecent fixture for my 55 gallon tank. The fixture comes standard with 2 10000k and 2 actinic bulbs. I believe the actinics are 460nm range. What value does a pure actinic light give? Would it be better to go with only 1 pure actinic and replace the second with a 50/50 or another kind of
bulb? I figure if I'm going to spend the money I should at least get the right kind of bulbs.

[Mzungu]

I know many will come on here to tell you that actinic lights are of no use whatsoever to plants. I don't agree. :)

460nm is a bit high for what I've read. I think I remember that after about 450nm, the light is less useful for aquatic plants. But they can still use it to some degree.

I'm confused on what your fixture actually has - does it have 4 PC lights, or 2 PC lights and you're counting the dual tubes that each "bulb" has as two different bulbs? I.e. are there 2 sockets in the fixture, or four?

If four, I would keep one of the actinics (they add good color) and get 3 other "plant type" bulbs. If two, you could use the actinic and a plan bulb, or switch to a 50/50 and a plant bulb. (50/50s are usually half actinic and half 10K or similar.)

[Darbex]

IMO I would go with the daylight and a "freshwater" bulbs or the pink bulbs. They make the plants look better.

[cichlid1409]

most green plants use blue and red light to accomplish most of their photosynthesis via chlorophyll A and B so with actinics providing blue light it shouldn't hurt thats for sure, but aestetically, it may not be pleasing.

[Complexity]

I figure if I'm going to spend the money I should at least get the right kind of bulbs.

Then you don't want actinic lights. Get plant bulbs (around 6700K, I believe). There are bulbs specifically for planted tanks. Combining two of those with your other two 10000K bulbs is a perfect combination.

[cameracorpus]

Before deciding to plant my 55g, I ordered Corallife 50/50 bulbs for the fixture. 2x55w bulbs. My plants are doing great. Only issue is BHA, which that tank had a history of anyway. For some reason that tank has always looked too yellow with 6700K bulbs. I know that's a personal preference, though.

[wesleydnunder]

From my reading and experience, plants do best with lamps in the 5000K to 8800K color temp range...don't know what that translates to in wavelength. All my tanks have 6500K or 6700K lamps. The one time I tried to incorporate actinics into the mix, and I really liked the colors it gave the tank, I had the worst outbreak of brown algae. I went back to 6700K and the brown algae went away. I haven't tried it since.

Mark

[Complexity]

For some reason that tank has always looked too yellow with 6700K bulbs.

That's why it's best to combine them with 10000K lights.

[Sea-agg09]

I had a brain fart, and it is 2 bulbs. Labeling says it comes with 1 actinic and 1 10,000k. I do agree that the low end is important as well. I am leaning toward the standard 10,000k bulb, and getting a 50/50 (10,000k/460nm) for the second slot. I figure that should cover most of my bases, getting in the low spectrum, but focusing more heavily on the high end.

[Mzungu]

Green plants really do seem to pop under yellower lights. If you can afford it, I think a good combo would be the 50/50 and a 6700K or even a Dual Daylight (Current USA's combo of 6700K and 10,000K, one of my favorites). The 50/50 and a 10K might be a bit blue, unless you prefer that, of course!

Since the K value in most aquarium bulbs doesn't actually have much to do with the spectrum of the bulbs, it all depends on the brand. Some publish spectrum graphs on their packaging and/or on their websites - I like those because you can really get a good idea of what to expect color-wise.

[Complexity]

combo of 6700K and 10,000K, one of my favorites

I have the same combo preference with Giesemann bulbs. Works very nicely for plants and for visual appearance.

[Sea-agg09]

I really like current-usa's CF bulbs. They have a huge selection. Just wish I could get better views of their spectrum printouts. Does anyone know whether splitting a single CF bulb into different wavelengths (i.e. a 50/50) gives you less light than a bulb that emits at only one temp? I would eventually like to have my two bulbs be a 6700/10000k and a 10000k/460nm, to ensure a good blend of light. While right now anything is better than what I have (single 20-watt florescent that came with the tank), so I can figure out what works best for me as I go.