ok, I am going to go a bit different, by not recommending 250 or 400, but rather find a bulb you like the look of first.
with the reflectors now days both will give you almost the spread you need, but if you have nothing on the sides then you don't need 36" coverage.
but seriously at 18" tall you don't need 400watts, the only reason to go to a 400 watt fixture would be if you like the look of the radium bulb, and even then you can have a darker radium or a lighter radium depending on if you run it on a normal 400 watt MH ballast or a sun agro ballast which used to be incorrectly called a 400 watt HQI ballast
my personal favorite was the Aqualine Buschke 250 watt 10K , but it is a SE bulb. I think it could be got in DE but the SE had a higher output. combine this with two URI super actinic VHO bulbs and you had a beautiful ice white color with lots of pop. weather you not you can still get these bulbs in Canada or not I don't know.
Start by looking at pictures of MH lit tanks and see what there using for there lighting equipment, find a look you like and go that way for bulb and equipment.
Steve
__________________
 *everything said above is just my opinion, and may or may not reflect the views of this BBS, its Operators, and its Members. If cornered on any “opinion” I post I will totally deny having ever said this in a Court of Law…Unless I am the right one*
Some strive to be perfect.... I just strive.
|