time for new bulbs

[babygeige]

I bought a 2 lamp HO T5 light fixture sometime in 2010, so I think it's time to change the bulbs!

It came with a 39 watt 6000K bulb and a 39 watt Rosette (that's all the info on the bulbs).

I read Carl's article about Lighting, and I'm wondering if I should stick with these bulbs or try something different. Is 6000K adequate, or do I need to be looking for something that is actually 6500K?

It's hard to gauge how much of a difference those bulbs worked, because my tank was such a mess when I switched fixtures. (I was using a Coralife CFL fixture, but didn't want to spend $70 on replacement bulbs). By the time everything got cleared up, maybe the useful spectrum of the bulbs had been pretty much used up. Right now I'm not very happy with the appearance of my 30's plants. They have decent growth, but the swordplants and anubias leaves turn black/brown after a while. It's very frustrating and I don't know what to do. I'm hoping changing the bulbs will work, but I want to make sure I pick appropriate bulbs.

[Carl]

6000K is good, but 6500K is slightly better (better depth penetration).
I would also suggest 100% 6500k, no Rosette

A Rosette (red) may be fine for terrestial plants, but under water it does not penetrate well

Actual energy output may also be poor, but this does not seem too likely with HO T5

I will state that the GroBeam LEDs and the SHO lights have produced ligating that is second to none with a lot of pearling on the plants.

Carl

[parker002]

My advice will differ from Carl's but only slightly. The Rosette bulb (likely in the 5000K range, like mine) has done absolutely WONDERS for my Red Ludwigia. Since starting with the Zoo Mod Flora Sun bulb, they've turned an almost irridescent pink.

Now, I use the 5500K red bulb (54W) in my Coralife next to a 54W 6500K bulb. Both of the 18" T8s are 15W 6500K bulbs.

I guess what I am saying is that there IS a use for the Rosette bulb but I would only use it if you're getting enough 6500K light elsewhere.

As for the Amazon sword and Anubias leaves turning black, that's not something that's simple to fix, even with the best lighting.

They grow slow and thus make a perfect spot for black algae. I've never been able to do anything to permanently get rid of it, I just prune it off when I can. Even spot dosing with Excel doesn't work on that stuff.

[Carl]

Good points Parker.

What I would like to clarify is that the red (Rosette) lamp is certainly an important aspect of providing correct PAR/PUR for plants, what I have found (& I suspect is the case here) is that if inadequate peak daylight lighting energy is provided due to too much of the lighting energy being of just red, certain plants will simply not prosper. Basically the "Phototropic response" part of the PAR equation is not adequate

As an example;
If you have two 15 watt 6500 lamps versus one 6500k lamp and one red lamp, I have observed better results with the first.
HOWEVER if you have adequate light energy 6500k from just on 15 watt lamp (a smaller &/or more shallow tank, since red does not penetrate well), then your other lamp is a red, this will likely give good or even better results, especially for tall plants that will grow toward the red light.

Another point I will make, is that with the LED now available, most sold for terrestrial plants have red emitters mixed in, YET the GroBeam 6500K does not and even though I have not personally done this experiment, I know of a couple persons that have and found better results and much more pearling with the GroBeam versus these greenhouse LEDs

Carl

[babygeige]

Thanks for the input, guys. I guess it's just going to be a matter of experimentation to see what works best with my tank. It's a long 30 gallon: 36 in long, 12 inches wide, 18 deep. So I thought the rosette bulb would be a help since it's not a very deep tank, but it didn't really make much of a difference when I installed this fixture in 2010. It didn't even affect the Red Ludwigia.

This time around I may see if 2 6500K lamps get me the results I am hoping for.