If your fluorescent bulbs are warm white, then all blue LEDs should be fine at half the wattage of the fluorescent. Otherwise, you might want to add some red or warm white LEDs along with the blue.

If you are considering using LED chips such as these,

http://www.ebay.com/itm/10W-365NM-395NM-UV-red-660nm-445nm-royal-blue-green-10000K-30000K-LED-light-bulb/291463169216?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D30424%26meid%3Dc1d9eb0a4c6e4eb382a8a14236153830%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D301623486723&rt=nc

then I point out that the red chips are typically more than twice as expensive as the blue or white ones therefore you could save money by using 3000 K white instead of red. Also, the 660 nm ones have a lower forward voltage, higher maximum current which makes it difficult to find a driver that will operate them at 10 watts. A typical 30 watt LED driver rated at 20-40 volts and 900 ma will operate three 10 watt blue and/or white chips or four 660 nm chips connected in series.

These 10 watt blue chips are even cheaper:

http://www.ebay.com/itm/Cool-Warm-RGB-White-30Mil-SMD-Led-Chip-Flood-Light-Bead-10W-20W-50W-100W-10000LM-/261635571617?ssPageName=STRK:MESE:IT&tfrom=261735590773&tpos=unknow&ttype=price&talgo=origal

Thanks aruzinsky, I haven't looked much at the 10W LEDs, I was thinking of using 3W LEDs like this:

Led World 10x 3W Blue LED 455nm-460nm

I figured these would make it a bit easier to control the heat. I'll read more into the 10W ones since they seem like a good way to save some coin.

I have similar aspirations. I plan to mount six 10 W LED chips on one 48" x 2.5" x 1/8" aluminum flat with a 60 mm cooling fan behind each chip on the opposite side of the flat, spaced, maybe, 0.75 inches from the flat. I currently have the parts on order.

Here is the aluminum flat:

http://www.speedymetals.com/ps-2229-28-18-x-2-12-6061-t6511-aluminum-extruded.aspx

Here is the fan:

http://www.ebay.com/itm/Desktop-PC-Case-DC-12V-0-16A-60mm-2-Pin-Cooler-Cooling-Fan-PS-/331555297949?pt=LH_DefaultDomain_0amp;hash=item4d323c5a9d

Incidentally, you can run a "10 watt" chip at 3.3 watts by using a 3oo ma driver. That's not very different than using a 3 watt chip.

I just now completed my setup but I won't be using it until April 2016. I can tell you now that the cooling fans are more than adequate. In these photos, all bulbs are LED:

http://www.general-cathexis.com/images/LED1.jpg

http://www.general-cathexis.com/images/LED2.jpg

http://www.general-cathexis.com/images/LED3.jpg

Thanks to Houss, two of these images wouldn't upload to Houzz so I had to put them on my website.

Nice work!
I'm waiting on the shipment of my parts, so hopefully I'll have a new LED build to show off soon.