J J Indy

I have a 55 gallon planted tank and I just started using the plant tabs to improve their growth which is working great but now my bulbs that came with the tank are going out they are T8 daylight bulbs that came with the kit i bought at petsmart. Getting to the question the bulbs dont have a Kelvin rating so i didn't know if it was the same as the 10,000k bulbs i have seen at the LFS does anyone know?

GreenMan13

What brand are they? "Daylight" is most likely 5500K or 6500K depending on the brand.

outlaw

Is there a name brand on the light anywhere? Bulb or encasement? Maybe you can search the manufacturer and find out what they come with.

J J Indy

thats a good suggestion to check the maufacturer to see if they list it. I was also reading another post about lighting and it sounds like i need more than 6500 for this tank for the plants.

outlaw

the 6500 is just the Kelvin spectrum of the light (different colors). Depending on the wattage and watts per gallon you currently have and the amount and more specifically the type of plants you have would determine if you need different bulbs. Before you buy higher wattage bulbs, may sure the fixture can handle it. From what I've been told and read, the bulb that usually comes with the fixture is already running at max wattage for it.

Hope this helps.

GreenMan13

Also, you don't really want higher then 6500K as it will have too much blue compared to the rest of the spectrum like yellows, reds and greens which most freshwater plants need.

mathas

I was under the impression that plants use blue and red light for photosynthesis, not red/yellow/green. In fact, don't most plants appear green because they reflect more green light than other colors?

In my opinion, color temperature can be a relatively poor way to determine whether a bulb is or is not suitable for plant growth. There are too many factors involved, and the marketed Kelvin rating is not always an accurate number anyway... most bulb manufacturers would rather market a bulb as 6500K than 7217K, or whatever the number may actually be. There are bulbs like GE's 9325K bulb, which has a good spike of blue at 400-420nm and a larger spike of red/orange around 600nm, actually gives off light with a more pink/red tone than the blue it's Kelvin rating would suggest.

GreenMan13

Plants need the full spectrum to be healthy including green but they only need very little green compared to other colors as the reflected green light shows.

For freshwater plants, ideally they would need a low K bulb which is yellowish in color to grow the most but this would require that you constantly clean the algae from the tank as this is very ideal for algae I believe. Moving up to the "daylight" range gives almost as much grow potential for the plants but not as much for the algae (algae use yellow light exclusively I think). Above this, and i don't mean just a 1000k or so but up past 10K you start getting blue color light which is similar to the light you see deep in the ocean as the salt water blocks most of the reds and yellow from penetrating deep. This is why there is little to no photosynthesis plants as you travel deeper and deeper in water.

Basically you don't want really low as it helps algae a lot and you don't want really high as you need a lot more wattage to provide the same amount of energy to the plant. But other then that you can lean on the lower side if you like a yellower color and on the higher side if you like a bluer color.

This is very true. Here is a graph of color temp. As you can see it is not very exact by any means.