Personally, I tend to use active cooling...
isnt liquid cooling a type of active cooling?if you wanted to use that thingy above, to cool RAM chips, LEDs, or really anything else that needs cooling, then you wouldnt just use it passively. it would be attached to a reservoir, pump, and a radiator. water would flow through the device, taking heat away from the chip.
Heatsink performance is measured in °C/W, which the above does not appear to specify in the link. Without this, it would be impossible to say whether it is suitable for LED cooling.
that is just one of many heatsinks/water blocks available fom the site, and that is only one in who-knows-how-many other sites on the web that sells this sort of thing, so there is probably some water computer cooling device out there some where that would be suitable to re-purpose for coolin' high-power LEDs
oh, and the particular cooling device i posted a link to above is intended for RAM chips which are shaped like a long-ish rectangle, so i thought that if it could cool them properly, then i could put a couple of LEDs in a row along it, to make a kind of LED strip-light. if i wanted a longer strip , then i could just put together a few more, and arrange them end to end.
another idea i had would be to use a bunch of CPU water blocks (which are usually square, like ordinary CPU heatsinks) , and have each one cooling a single tri, or even quad LED, and position them over the plants. then i would just connect them all together with tubing, and attatch the whole thing to a reservoir, pump and radiator.
i got the idea to use some kind of water cooling system because i wold rather use tri, quad, or other multi-LEDs so that i wouldnt have to worry as much about color blending. these kinds of LEDs throw off a lot of heat, and these type of cooling systems are used to cool CPUs, some of which can get pretty darn hot, about as hot (probably hotter) than these LEDs, so it seemed like something that might be a good way to keep the lights cool. i take it that no one on here has tried this? might be worth a shot, ya never know 'till ya try...