The Kelvin ratings for CFs are related to the ratio of redish spectrum (700nm) to bluish spectrum(400nm). the Ratio is balanced at about 6000 Kelvin. I have had 10k Kelvin bulbs in two of the slots in my hood, Do I need 10k bulbs?or is it a waste? I have a ballast that controls six 96 watt bulbs,two are actinic (cause the cool looking) and the others range from 6700 K to 10k K. I think it's about time to make some switches for new bulbs, because they have been in for a while. Should I replace them all at once or a couple at a time? 5000 K bulbs or 10000 K bulbs. The Actinics can stay for now...

For the best plant growth and general appearances, you want weak blue light and strong red light.

So the 5000-6700K as a primary source and then perhaps 1/4 10K lighting would do fine.

The Atinics blue band is too narrow(pretty much a single narrow spike) and really make the tank look strange. It's fine for marine systems where the light filtering is stable and the corals come from defined depths.

Regards,
Tom Barr

I'm convinced that your choice of K ratings for bulbs is just a personal preference issue. In fact I asked some time ago if anyone had ever tested actinic bulbs to see if they really were of no value to the plants, and no one had. So, use whatever bulbs makes the tank look as you want it to look. I'm not clear yet on what the life limit on PC bulbs is. I used my 55 watt bulbs for about 15 months, and they didn't seem to be any different at the end - but I admit when I replaced them with 36 watt bulbs I couldn't see much difference.

Does anyone know of any T8 tubes that cover about the 10k range? most ive found are 6500k providing no red spectrum at all, or 18,000k and provide too much giving me algae problems, (brown, GSA).


Ive retested my earlier experiments with lighting colour now my CO2 is stable and therefore, comparible. Ive found that running 2x 6500k and a 18,000k produces no more pearling than running 3x 6500k tubes, under the same conditions.

Im not overly sure why that would be, you would think that the tube with more red spectrum would lend the plants to photosynthasis at higher rates.

It seems like those 2 statements would contradict eachother, but I do find that the algae prefers the 18,000k even more than the plants seem to.

Worry less about algal observations and more about what the plants prefer.
That is your standard.

Regards,
Tom Barr

The higher the Kelvin rating of the bulb the more blue vs red the light will be. Red is relatively low K and blue is relatively high K. That's why bulbs for salt water tanks are high K and blue.

An easy and interesting experiment someone could try is two identical tanks, one with a half actinic bulb and one with 6500-10,000K bulb, and see what the differences are in plant growth in the two tanks. If the often repeated statement that actinic light does no good for the plants is true, then high light plant species will do much better in the tank without the actinic bulb.

So, I should put basically any combination of lighting as long as I can control the parameters and control the growth patterns in the plants, so to speak. That makes sense, the 5000 to 6700 are more or less full spectrum where the 10k bulbs are more towards the red end of the spectrum?
On Actinics...what about the bulbs that are multiple color blue violet that cover 400 to about 500? stillno use to the plants? And at that point is it just asthetics?

I can't vouch for what spectrum the plants use since I'm brand new to the whole planted tank thing, but I will agree with Tom's earlier post that the actinics just make things look a bit wierd in a freshwater tank. My T5 retrofit came with two 10000k and two actinics and my tank has a blueish tint to it that bothers me. After reading this thread I just ordered a pair of 6000ks to replace the actinics.

Aaron
180 Gallon freshwater w/plants on order

Just My own observations:

5000 to 6700K is a given for useful lighting for FW planted aquaria. 10,000 can be useful for deep tanks, High light plants, and midday spikes in lighting cycles. As Tom said no more than 25% on 10,000K and then only with 30 to 40% Co2 ! I have found the Colormax tubes to not only be helpful for red spectrum loving plants (IE: Rotala/Lotus etc...) and of course better color rendition, But never more than 15% or they can contribute to algae growth.

Honestly Actinics, and Royal Blues serve no useful purpose in FW planted aquaria unless your goal is cultivating Algae.

I wrote the book on "Aquarium Lighting for the Criminally Insane" ! Once you exceed 2.75 to 3 watts per gallon your time and money would be better spent on quality lighting Components. Ballast/Reflectors/Bulbs/and low voltage fans. (AH supply is an excellent resource)

Better Co2 system components certainly wouldn't hurt, and a decent drop checker will allow you to accurately administer the Co2 levels. If You Just gotta spend money on the tank splurge on some TMG, or better substrate IE: ADA AS, Seachem Onyx, or Flourite.

The only thing that excessive lighting gets you is Algae, and a High utility bill. HTH Prof M

That's good info Prof Meyers, specifically about the 10000k lights. My tank is 29" tall x 60" wide by 24" front to back. Perhaps I'll use the 6000k dual bulbs for the long stretch of light and just turn on the two 10000k units for the midday light. That would be more like 50% from the 10000k specturm but only for midday and since my tank is a bit deeper perhaps it will be a good mix.

My total wattage is 320 (4x80) so 1.8wpg with all the lights running. My tank is in an enclosure (built into the livingroom wall) and I am finding that the heat generation from the lights may be an issue. Even with just one set of T5s running the temp in the enclosure gets above 80 deg F. I think I need to ventillate somehow.

Aaron
180 gallon Oceanic Freshwater to be planted this weekend!