which t5 ho tubes are best??

[bobchick]

Hi,

Im after getting lighting for my orchids. I find it all rather confusing. I have looked up hydroponic lights and they all seem to recommend the lights be just a couple of inches above the plants this is not what I've seen with orchid growing.

I was thinking to just buy some aquarium T5 HO 24W lights but confused as to what tubes to get 18,000k or 67,00k or a combination of both

So guys come on, whats with the distance of hydroponic lights to plants? Is aquarium lights ok? What tubes are best?

help and advice please???

cheers folks

[jmmehler]

Search for the thread 'First T5HO Light' on this site. You should be able to glean all you need from there.

[Subrosa]

Much hydroponics info is geared towards growing cannabis which is a full sun loving plant. Most orchids prefer lower light levels. Aquarium bulbs work but tend to be pricier than bulbs intended for terrestrial plants. If you go the aquarium bulb route, stick with K values under 10,000K. Higher K values are much bluer and aren't helpful in getting plants to bloom.

[jmmehler]

Sorry, I believe the 10,000 value referred to is to foot candles, and not K (Kelvin temp).

The T5 HO bulbs are either 5,000 or 10,000 Foot candles each. Can't recall which.

They come in various temperatures listed as K for Kelvin. for blooming, the 3,500k is preferred. For growth it is the 6,000k. I always get a combination. I keep them about 6 to 8 inches above phals. If they get over 8 hours of light pre day, they develop what I consider a beautiful sun tan, or blush, in the form of some reddish hues in the green leaves.

The bulbs do loose some intensity after a couple of years but still function well. replacements are about $6 per bulb. Found a site where they were $1.37 per bulb, but came in a minimum of 40 per case. Guess what? I now have 40 each of 3500k and 6000k. A lifetime supply.

[naoki]

In aquarium shop, they charge a lot of money, so you might want to check you can find these cheaper "plant" T5HO from eBay.

Mine is by Odyssa, and it gives more plant relevant light than the "white" bulbs according to my measurement:
Cheap T5HO "Plant" bulbs and longevity

To your eyes, these plant bulbs look dimmer, but plants are getting more relevant light.

The distance depends on what plants you are growing etc.

I noticed that you were talking about the "best", so the cost may not be relevant for you. Here is a calculation done by some Planted aquarium people from South Africa to find best bulbs. It is sorted from the most efficient to less efficient (the top is the best). Basically they digitized the emission spectra, and calculated how much plant relevant light is emitted for a given amount of electric power usage. This is the "PAR efficiency" column (micomol/J is the unit). K (kelvin) column is the calculated (not the advertised) corrected color temp. This is a bit old data, so I'm not sure if all of these are still available. To be honest, I'm not sure if the PAR efficiency of the top one is really correct. It seems to be too high for fluorescent light.

[Subrosa]

Originally Posted by jmmehler

Sorry, I believe the 10,000 value referred to is to foot candles, and not K (Kelvin temp).

The T5 HO bulbs are either 5,000 or 10,000 Foot candles each. Can't recall which.

They come in various temperatures listed as K for Kelvin. for blooming, the 3,500k is preferred. For growth it is the 6,000k. I always get a combination. I keep them about 6 to 8 inches above phals. If they get over 8 hours of light pre day, they develop what I consider a beautiful sun tan, or blush, in the form of some reddish hues in the green leaves.

The bulbs do loose some intensity after a couple of years but still function well. replacements are about $6 per bulb. Found a site where they were $1.37 per bulb, but came in a minimum of 40 per case. Guess what? I now have 40 each of 3500k and 6000k. A lifetime supply.

10,000 is definitely the K value. A T5 tube that produced 10,000 fc would be a lot longer than 4'.

[PurpleOrchid]

I just set up my t5 HO light fixture. Should I start out higher and gradually lower it? Or is it ok to just set it low? How many inches away from plants is good?