I know I am an unknown here but having done extensive researched on growing

aquatic plants under lights. I am sure you may well be well beyond my current level of understanding and I have many questions that I am sure you could answer
for me. However if you are in search a fluorescent bulb with a high rendering index with a full spectrum out put, I would fist ask what color temperature do

you need the bulb to be. Some plant only need 5700 degrees K some may do

better under 8000 degrees K. The more complete and the quality of the rare earth

ingredients present in the bulb will give you better results for a longer time.

The most important number is the color rendering index, if it is below 80, the color

spectrum will have veritable holes in it.

This is the link to one good supplier in the USA.
They should be happy to answer your questions, they have the best bulbs, and likely the best price. This is my fist post so I hope it has given a bit of help.

These bulbs are around ten US dollars.

http://www.thatpetplace.com/Products/KW/FISHPROD%2cT-8/Class//T1/F55%200495%200209/Itemdy00.aspx
The color temperature may be too low.

http://www.thatpetplace.com/Products/KW/zm0217/Class//T1/F55+0495+0217/EDP/23820/Itemdy00.aspx

The color rendering index Ra on this one is 97 very acceptable and it is at 6500 K almost the best you are going to find for a grow light. Rare earth is what makes the CRI and that is what you are paying for make no doube and the ones a regular store know people don't know about CRI so why sell it. Wow I wrote all this I didn't notice you were in England. I have no idea if they will ship to the UK but my guess is that they will, because they are a giant store in the US. The next time you pop over the pond to do some shopping, at these low US prices, you may stop by as this store as it is one hell of a good show
This a great link for some lighting terminology:

http://www.schorsch.com/kbase/glossary/cct.html

Good Luck,

Here is a link that might be useful: That Fish Place That Pet Place

Unfortunately I'm in the UK, hence the problem with different brands. I thought that colour rendering index was only to make the tube more visually appealing, it had little effect on the actual radiation transmitted?

RP1

What are you trying to achieve? Maximum useful light for the plant? Best colour rendition for your own eyes? Simply the most light for your pennies?

How flexible are you with fittings? You will be able to get a decent range of special-spectrum 48" tubes by buying online, but the range of compact fluorescents available in the UK is very restricted other than the household warm whites. I can show you a few sources if this is what you wanted.

How much light do you need for your setup? You have space for about four 48" tubes, maybe six if you go to T5, but note the standard T5s are actually longer than 48".

color rendering index or Ra is a rating that tells how well a bulb duplicates sun light. Light is measured using two methods, wavelength and frequency. The wavelength unit of measure = nm or mm, Frequency is how often a wavelength occurs with in a second (time), this unit of measure is give as Hertz(Hz) or in other words the number of vibrations with in a time span of one second. One Hertz = one wavelength in one second. If we look at light in Hz Blue light is 6.5 X 10 to the 14 th power. When we look at a rating of color temperature or Kelvin we are look at an over simplification, the lower the K the warmer, the higher the K the bluer or cooler the light is, it is used primarily for architectural lighting design and photography. I have used a light meter and the highest K I have ever gotten at home is about 7000 K, I don't like this way of measuring the magnetic spectrum of white light for the growth of plants, as it tell me nothing, so they threw in the wording, Full Spectrum. I prefer Wavelength, but K is somewhat directed toward Hz. If you get a light source rated at 6500 K it may not render 4500 K if the CRI is less then 80. Your plant may need that light spectrum to bloom or to do what ever it needs to do. Noting is comparable to natural sun light but we do the best we can. Full spectrum is most related to CRI, as full spectrum should be a light source rendering(yield) light from Infra Red A, to Red, Orange, Yellow, Blue, Indigo, Violet and hopefully a little bit of UV A and B.
I hold a degree in science ,majored in physics, concentrations on light,optics, mechanics, thermodynamics, and electromagnetism. Yes CRI is very important. I don't know what is on the general retail market but I hope this helps.

There'll be orchids in there so I'd say light in the region of 2000fc possibly more @ ~6-12" from the fixtures at most?(I know it drops off exponentially)

Couldn't give a damn about colour rendition, more light in the suitable frequency is what counts, even blue spikes seem difficult to find on most tubes, let alone reds.

Envirolites are the only cfls I'd consider, and they are either in 2700k or 6100k, so I figured if I had one of each, that would be enough light in the usable spectrum, but heat would factor in, since it would be a sealed but ventilated tank.

I thought the aquarelle since it had the biggest peak I've seen in the blue spectrum, gro lux for red(considered a wide spectrum but they're t12s).

I've heard a lot of things, namely that the colour spectrum isn't as important as lumens, so would you opt for standard triphosphors or halophosphates or more specialist tubes?

Deshima, a lot of that radiation just isn't used by plants but is visible to the human eye or suitable for reptiles, so is full spectrum really beneficial at all for plants?

Cheers

RP1

I also guess since it'll be a terrarium with waterfalls, ferns, carnivorous plants, orchids, stream, cliffs and trees, that maybe a gro lux with its pink coloured light wouldn't exactly be too ideal for looks.

Is the aquarelle a more blue coloured tube than daylight?

RP1

For a terrarium with orchids, I say look into getting CFL bulbs. I realize you're in the UK, and you may not have access to the myriad of bulb selections we here in the US do. I have a tank your size, with CPs and orchids in it, and I use 2 85W CFL bulbs. Both in 6500K-the maximum in color temp I would suggest for plants.

Great light, great looks, great growth. You may also want to look into T5 HO lights, but they are more expensive.