metal halide bulbs

I've been growing with cfl's and considering going MH and Hp. I found a 250 watt MH that the seller is calling aquarium lighting, he has bulbs rated 20,000K but the add doesn't mention lumens. Is this bulb good for veg grow or is it specifically for aquariums? Didn't know if Posting link is allowed so I just posted description. Any help is appreciated. thanks.

Brand New in box

250 WATT METAL HALIDE

Metal Halide bulb

MULTIPLE COLORS AVAILABLE- PLEASE CHOSE COLOR DURING CHECK OUT

WE HAVE:

10K- CRISP WHITE COLOR

14K - WHITE COLOR WITH A TOUCH OF BLUE

20K- DEEP BLUE COLOR

Will provide amazing coral growth while bringing out the attractive colors on your fish.

Shipping - $4.99 anywhere in USA

Canada - $13 for as many bulbs as you need

all bulbs shipped insured so breakage is not an issue

Can anyone explain the difference (other than price) in the bulb mentioned above compared to a 250 watt hortilux with the following features? Are bulbs that say aquarium lighting not usable as grow lights? richinweed can you elaborate on why not to do it?

Lamp Features:

• Manufacturer: Eye Hortilux
• Model: MT250D/HTL-BLUE
• Wattage: 250W
• Lumens: 18,000
• Color Temp: 6500K
• CRI: 90
• Finish: Clear
• Base: Mogul E39
• ANSI Code: M58
• UPC Bar Code: N/A
• Burn Position: Universal
• Bulb Life: 10,000
• Price Shown: Per Lamp
• Case Qty: 12
• Lamp Shape: T-15
• Length: 9"
• Width: 3"