LED fan question

[dputt88]

so i have a few old reef breeders that i was modifying so i could mount them to t-slot aluminum. when i opened them up there was a pile, yes a pile, of dist on the heat sink. this was caused because the fans blow inward and directly on the heat sink. is this the correct way to position the fans on LED lights?
Also, is it worth while to flip them around?

 

[saltyfilmfolks]

It’s better to blow into a box than out.
It moves more air.

If you know someone who smokes , you can do an experiment with a clear soda bottle.