New light bulb for my tank?

[RnLGG]

I have a 35-gallon Hagen tank I got from a friend around six months ago, and I've never changed the light bulb in it. At first I thought the light was just a low-power one, it was a kind of purple colour. I eventually decided to take the bulb out and find out what type it was. Turns out it was an aqua-glow bulb, which "Intensifies fish colors and promotes plant growth" I guess my bulb is really old since it's so low-light. Does the Aqua-glo always have a purple tint to it?

I'm going to get a new bulb today, and I was wondering what to get; either a new aqua-glo, or a power-glo, or whatever will suit my needs. I can only have one bulb, and I'd like it to be bright to match the tank below it. In the tank there's java fern and java moss, which are low-light plants, so maybe a really bright light isn't the greatest idea? Fish-wise I have a chinese algae eater, they like bright lights, and odessa barbs, which would look great with bright lights.
It'll be a great help if you could help me decide, thanks!

 

[fort384]

If it is a stock light, then then you aren't going to be able to get a bulb that is "too bright" for any live plants, even low light plants. It doesn't have to be aqua-glo or power-glo, but for the plants the color temp of the bulb needs to be somewhere between 6500K-10000K. That is really all that matters. Most likely you aren't going to be able to adjust much else about it... the wattage will be standard.

 

[jsoong]

A lot of the plant bulbs have a reddish tinge to them, the red spectrum is supposedly good for the plants. However, it makes the bulb look dim to our eyes & sometimes give a weird color cast to the fish. A lot of people have one plant bulb & one 10000K to offset this effect.

For a one tube setup, I would go for a day-light full spectrum bulb in the 6500K range. This should give you the best combo of looks vs plant usable light. <And no worries about low light plants ... stock lights will not get to even low light level, and most low light plants (like yours) are classed as low light because they can survive in low light. They actually grow better with a bit more that the minimum.>

 

[RnLGG]

Alright, I looked at all of Hagen's light bulbs, and I think the "Life-Glo 2" best matches what you guys said I should aim for; It has 6700K. I looked in on the old bulb I have, it's 18000K, just a little too high! I've got no knowledge about lighting, but does the Kelvin go down as the bulb ages? Or what causes it to go dimmer?
Thanks for getting me on track!

 

[jsoong]

The K doesn't necessarily goes down, but it does change with age. After 6-12 months, a bulb's spectrum is no longer the same as new. The dimmer part is the phosphors wearing out, and the bulb is actually putting out less light than before.

 

[RnLGG]

Thanks you two, +1 to both of you. The bulbs between 5000-10,000K give off a neutral white light, which is what I was looking for. Anything lower is red/yellow, anything higher is blue/violet. I've got nothing in my tank with specific needs for having those, and I think the white light is more appealing to the human eye.
Once again, thanks!