Time for new Bulbs

[Lpabsolute]

Hey guys, i'm currently running a 250watt MHL 20,000K pendant over my 54 g open top reef. The bulb is almost a year old and i plan on changing it soon. My question is what's the difference between the "10K, 14K, 20K"? i know they look different but which do you prefer. Would my tank be ok if i switched from a 20K to a 14K? Just trying to decide on what to do. If anyone out there has any pics they would like to share of thier MHL's or can show me the difference between the bulbs i would appreciate it.

[rwessels]

Generally the lower the K, the whiter and more PAR the light has. Many people like 14K as it is a nice medium. 10K usually has the best growth though.

[Lpabsolute]

Just ordered the Phoenix 14K 250watt bulb and it should be here by Monday.

[Sullyman]

I hope you know they only last about 6 months.

[Lpabsolute]

What do you mean they only last 6 months?
I thought the average life on MHL bulbs are 12 months....

[stewie24]

It depends on how long you run the lighting, but MH bulbs tend to shift spectrum / loose par after 6-8 months causing unwanted algae growth. If i were you i'd go to lowes/home depot and buy a section of window screen and throw a layer over your tank for 4 days or so - so you don't blast your corals w/ a higher par lamp. A 20k bulb doesn't have as much par (brightness / penetration depth) as a 14k bulb. Also a year old 20k bulb wouldn't be anywhere as near as bright as a new 20k bulb. Since you stepped down from 20k to14k, I'd either do the window screen or raise your fixture 4-6 inches and then slowly lower it down to where it was over the period of a week or so.
Good Luck.

Stewie

[Lpabsolute]

I was told at my LFS that i would be ok switching from the 20 to 14, and they suggested to just cut back the hours i run the lights and keep moving them up. I run my lights now from 1-11. They said to run they only for a like 4 hours a day for a couple days and keep uping the hours until i get back to where i was. Is this a good idea?

[stewie24]

That is one way of doing it although not preferred. Even on for 4 hours might cause some harm. Imagine yourself being outside for 10 hours a day during a semi cloudy day for a while, then the next day being outside in full blast sunlight for 5 hours. You'd probably end up getting sunburnt (or tan). That would be the same with the corals. You want to give them a little more light then let them get adjusted to it (get tan instead of burnt). I'd recommend the window screen or raising the light and slowly lowering it say an inch per day for a week. (5 days)
Stewie

[Lpabsolute]

What kind of window screen do i need? And how would i use it?

[Sullyman]

Any non metalic screen will do, it will block some of the light.
Do a search on Phoenix 12k in the Lighting forum, these bulbs have an average 6 month life.

[Lpabsolute]

I didn't order the Phoenix 12K, i ordered the Phoenix 14K and everyone i talk to who has them and has had them in the past say the average is 12 months....

[Sullyman]

I meant 14k and there are a few threads about the bulbs life span, concensus seems to indicate a 6 month life span.
It was either in the lighting or sps forum, long thread.
The offset was the lower price, around $60 a bulb.