hi,

thinking of putting up 3 x 5ft tubes in my conservatory for extra light in the winter, what kelvin rating would be best for citrus?

I think the aquarium trade has "plant light" fluro tubes with better spectrum for water plant growth. Maybe check out that line of investigation ?

I use one of this type and it works well.

How often do you keep the lights on for? Is it costly on the electricity?

17h by day. It is 30W, so it might not cost much.

30W? Doesn't sound much, you thinks it's made any difference?

I only use this tube for the seeds and seedlings. The whole is covered with aluminium sheet (I don't know the name, safety blanket?). It is very bright under it.

thanks for the replies, i have found some 58w growlux tubes on the net

How much did they set you back?

There are some FL Tubes that are not marketed as Aquarium lights and they costs less but put out the same type of light. I don't have access to my research I did on this but what you are looking for is one with a higher color temp nad possibly one that leans in the red or blue wavelengths. I'm sure if you did some Googling or Yahooing you will find some research on color temps and color as it relates to citrus seedlings and plant growth. The resaon for getting away from the Aquaririum bulb is the cost. Much cheaper if it doesn't say plant or Aquarium. You might find the research on an Aquarium sight.

When I was researching them I was looking for one for my planted aquarium. I found one at the big orange box store that was nearly identical and costs 30% of the one at the aquarium store. It would work for terrestrial plants as well. Look at the specs on the plant bulb and then go compare them to what they have available at the box store.

Here is a discussion on flourescent bulbs and plant growth.

http://www.gardenguides.com/88912-fluorescent-bulbs-plant-growth.html

Hope it helps!