the deal with barbs/fittings for pumps?

i tried searching for this, but i couldn't find any good combination of "what barbs fittings" in the search that wouldn't yield a thousand or so posts, that didn't deal with this...

i was thinking of getting the eheim 1250 pump from criticool.com (as i've heard they attach the barbs/fittings already) but for my setup, i'm thinking i'd prefer the eheim 1048. now, i can't seem to find a canadian retailer that sells the 1048. so i was considering trying to buy it at a pets/fish store of some kind.

however, i'm not quite sure what the real deal is with barbs and fittings. do you have to add these barbs/fittings (i'm not quite sure what the difference between these two terms are so i'm using them somewhat interchangeably) to a pump to use them in watercooling? different posts have given different accounts. as well, when i was considering the criticool's watercooling kit, which uses the 1250 pump (3/4" and 1/2" OD intake/outtakes), it included a 3/4" - 1/2" barb adapter and a 1/2" - 1/2" barb "adapter". it's this second one that confuses me, to use 1/2" ID tubing, why would you need a 1/2" - 1/2" barb fitting if it's already 1/2" OD? which is why i'm wondering if maybe you have to add something to the barbs on a pump anyways to get it to work with watercooling...

i guess what i'm really asking here is if i buy the 1048 at a pets store (which uses 1/2" OD barbs for both), do i have to add any "fittings" to it to get it to work with 1/2" ID tubing? thanks

Buy it online if you can.

On my 1250 I didn't get any special barbs, only the stock ones.
1/2" and 3/4"
Other than the fact that it took some straining to get the silicone tubing onto the 3/4" barb, it was fine.