vivarium light and humidity question

[leigha]

Hi Guys
I had previously posted a thread askign for help with my new 20 gallon vivarium thank you for all the responses and help)...now it has been a couple weeks since the set up, I have a coup,e more questions...
1. light: I am curently using a fish tank canopy - 2, 24" T5 bulbs (not sure the K rating - I suspect between 5 and 6K). They seem to be emitting enough light, my Brassia has now developed a slight "tan". Are 2 T5 bulbs enough or 2 more will be better..I also have seen T5's rated at
10 000K!! Mimic for sunlight - will these burn my plants if I decide to replace the ones I have?

2. Humidity: I currently maintain daytime humidity between 50 to 60% - (small computer fan circulating air). Is this high enough? Was thinking to add humidifier to direct mist into the viv. Or do I ven need this? My mounted orchids do dry out quite quickly (within the day)

any input greatly appreciated!!
thanks so much

[Ray]

Two bulbs are probably sufficient, depending upon the distance to the plants. I have 3 such lights in a 20-gallon terrarium of jewel orchids, bulbos, and a couple of others, and had to elevate the lights to roughly 18" above them to prevent burning.

Higher color temperature does not mean they're better. Something in the area of 6400°K most closely mimics direct sun plus back-scatter from a blue sky - AND the absorption spectrum of chlorophyll. 10,000°K shifts the spectrum so far into the UV that is is of very little value to a plant at all....they are meant for coral.

Your humidity is sufficient. Mounts drying within the day is perfect!

[leigha]

Awesome, thank you! I also have bulbos and a couple of jewels (along with some others)...I will leave my set up the way it is for now. The only thing I will monitor is the distance to the plants - my plants are 8 to 14" away from the light source - haven't noticed any burning yet, but will see. Thanks again.

[King_of_orchid_growing:)]

50% - 60% RH is adequate enough for most orchids. There may be other types of orchids which may have higher demands. You must be aware of the kinds of orchids that you're purchasing and what their needs are.

10,000 K is usually designated for corals. The reason being is that it is trying to mimic the wavelengths that are filtered and allowed through by the saltwater at a certain depth. The primary wavelength of light in the color spectrum that saltwater allows through down to a depth of roughly 60 m is blue. Wavelengths of visible light in the color spectrum that saltwater filters out at relatively shallow depths are red, yellow, and orange. Lights with a Kelvin temperature rating of 10,000 K emit more blue than any other wavelength of light in the color spectrum.

A Kelvin temperature rating of lights for plants in a vivarium of anywhere between 5,500 K to 6,700 K is adequate. Lights in the range of 5,500 K to 6,700 K emit a broader spectrum of wavelengths of light in the color spectrum that is closer to what natural sunlight produces.

Although T5's are sometimes used for growing certain types of corals, I feel that these lights are not intense enough in maintaining the long term health of many of the corals available in the mini reef hobby. But they are fairly adequate in growing some of the more light demanding freshwater aquatic plants. The reason being is that freshwater is less dense than saltwater and will filter out less light.

For the use of lighting vivarium plants, 2 T5's are pretty adequate for growing many types of orchids (air is less dense than water and will not filter nearly as much light as water does), although there may be some orchids that may demand more light, and that is where the knowledge of your plant's needs comes in.

[tropterrarium]

Agree with previous posters on the 10K comments.

Re RH, depends a bit what and how you grow them. If you have mostly potted plants or some with lots of moisture retaining material (short of causing root rot), then 50-60% should be fine. If you grow mounted on sticks and bark with bare roots in the air, I would go higher, in the 70-80% range.

Re light intensity and tan, note that the given footcandle (fc) ranges for a given species is for peak natural daylight. Daylight is however weaker in the morning and the afternoon. Terrarium light is ON 100% (there are a few options for dimmers, but I have not heard of anyone using them) or fully off. So to get the approximately same amount of light over the course of the day, terrarium light should be about at half-intensity of recommended out-door light. I've mathed it out, using semicircle, parabola and Gaussian curve as proxy for natural light intensity variation over the course of a day, then converted the area to a rectangle with same base length, and unknown height (= intensity of terrarium light). Math will be on-line in fall with AOS.
Now you only need a way of measuring light intensity. There are a number of options from plant light meter, photographic light meter to iphone app.