This 400 watt light bulb is amazing needless to say and love how easy it is to light up my 93 gallon cube. I run this bulb on a HQI PFO ballast like recommended. I have had this bulb for a year and believe it has lost its power of growing corals 6 months ago. I have read many places that these bulbs should be changed out every six months and that's ok. I love the look and my corals love them. I am going to experiment and try the Megachrome Crystal SE 400 watt which was made specifically for a 400 watt HQI ballast and said to last twice as long. Its more expensive but if it lasts twice as long is it???? Looks like $25 savings every 6 months. but if that doesn't work I would gladly pay more for the Radium.

Great bulb. The only downfall is the price but I guess you have to pay a little more for an awesome bulb. Nice crisp color with some blue. I run them on Blue wave 7 ballasts. Love it. No supplements needed.

This is a very good bulb but the color is quite a bit more blue than I like. It really makes the corals pop and gives a nice shimmer effect.

in my humble opinion this lights are the best outhere i hope they could cost less because of the leds but it seems the quality of this bulb dont allow the price to low

coloration of this bulb is very good for corale maintain backward sps

These bulbs are not that much more than many of the others out there and the corals love them.

I had used "blue" and "purple" T5's before switching to Halides and this bulb gives off the most intense, blue light I've seen. It's working well.

I ordered 1 radium to go with the 2 I already have and shipping was fast and it was wrapped very good thank

This replaced a ushio 20k 400 watt bulb, The ushio is not a bad bulb at all, but this has a lot more brightness to it, completely beautiful color to it. I wont need any other bulbs except this now.

Wow, this is supposed to be a 1000w bulb??? We were forced to replace our Helios 20k bulbs as they have been discontinued, but excited to find the Radium makes a 1000 bulb! That excitement was quickly extinguished once they fired up... These things are no where near as bright as the Helios we just replaced. Good color, but no where near the brightness I would expect from a 1000w bulb. :( Disappointed not only by the lack of light, but since they were twice the price of a Helios, it makes it sting even more.

Used this to replace another 250w bulb and it's night and day difference. The corals are all more colorful and growing much better the before. The blue tint is exactly what I was looking for.

At least when run on proper HQI ballasts, these give off about 270 watts of the most beautiful 20,000K light I've seen - can't beat it. On plain electronic or other magnetic ballasts these bulbs (150w DE or 250w SE) may be under-driven and give off a much more blue cast - too blue to most people's eyes.