There is no good answer for this question, especially when you are planning on using LED fixtures like the one you linked. Using those kinds of lights is just fine, by the way, and a good idea in general.
Here's why:
LEDs will vary significantly in their efficiency. They do tend to be more efficient than most fluorescent lights, but ones with small emitters (under 1 watt each) just don't have the punch we need to put light on the sandbed.
I own a white 7 watt PAR30 bulb that has 25 or 50 (or more..??) LEDs. At 7 watts it barely farts out enough light to be used as a night light in my toddler's bedroom. Actually works quite nice for that.
Yet if I were to put in there 7 watts of high power LED (say, a couple of Cree XPG) then I could easily read a newspaper from 10 feet away. Very bright.
The lamp you linked only uses 4 watts or so but has 20 LEDs on it.
Trust me, it won't work for any but the most low-light plants, and even then, I wouldn't bet on it.
Look for bulbs that have, preferably, 1w or 3w LEDs.
From there, assume that you'll need to get roughly 2 "watts per gallon" for a medium light situation. But I say that with no guarantees since these lights can vary a LOT in their build quality, LED brand/color temp, and drive currents.
If you don't mind spending the money, go to www.nanotuners.com and browse their "Evil" Par38 lamps. They are made for reefs but I think you can get them with all white, or you can go with the 12K look (which you may not like, it's quite blue).
If you got the Evil PAR 38 bulbs, get ones with 80 degree optics, or get 60 degree optics and hang the lights VERY high for a good light spread. Either way you'll be playing around with hanging-height to get the light spread right.
You'd want at least 2, probably 3, to avoid spotlighting. Not cheap, but these are very well made lights.
Here's why:
LEDs will vary significantly in their efficiency. They do tend to be more efficient than most fluorescent lights, but ones with small emitters (under 1 watt each) just don't have the punch we need to put light on the sandbed.
I own a white 7 watt PAR30 bulb that has 25 or 50 (or more..??) LEDs. At 7 watts it barely farts out enough light to be used as a night light in my toddler's bedroom. Actually works quite nice for that.
Yet if I were to put in there 7 watts of high power LED (say, a couple of Cree XPG) then I could easily read a newspaper from 10 feet away. Very bright.
The lamp you linked only uses 4 watts or so but has 20 LEDs on it.
Trust me, it won't work for any but the most low-light plants, and even then, I wouldn't bet on it.
Look for bulbs that have, preferably, 1w or 3w LEDs.
From there, assume that you'll need to get roughly 2 "watts per gallon" for a medium light situation. But I say that with no guarantees since these lights can vary a LOT in their build quality, LED brand/color temp, and drive currents.
If you don't mind spending the money, go to www.nanotuners.com and browse their "Evil" Par38 lamps. They are made for reefs but I think you can get them with all white, or you can go with the 12K look (which you may not like, it's quite blue).
If you got the Evil PAR 38 bulbs, get ones with 80 degree optics, or get 60 degree optics and hang the lights VERY high for a good light spread. Either way you'll be playing around with hanging-height to get the light spread right.
You'd want at least 2, probably 3, to avoid spotlighting. Not cheap, but these are very well made lights.
