I have a 245 gal freshwater tank. Water change every 2 weeks, 1x a month the fuval fxs gets cleaned and the 2 aquaclear 100 every 2 weeks, temps nice and warm at 82-84F. Water is straight from the tap WITH seachem prime as the water treatment. Tank has 1 FRT, 6 various sized discus, 1 large very old pleco, 1 banjo catfish, 1 bushy nose catfish, 5 clown loaches and 2 giraffe cat fishes.
The giraffe fish need plenty of hiding spaces, they rarely come out of their hiding spots- which I have many in the tank for them to hang out. The ones i have are about 6-7 " long and seem not to get any bigger, had them for over 4 years, doing great, very peaceful fish. The only exciting time is when they engage into a pushing match with each other in their favored "tree root" house. Mostly I feed them the Hikari algae wafers which they share with the FRT, clown loaches, and other cats. My giraffes don't bother any of the fish. The most delicate fish in my tank are the discus and they are the tank clowns having a ball racing around the tank trying to get a human to feed them.
My present 2 giraffe fish must be from the smaller variety....
I want to WARN YOU that there are a LARGER kind of giraffe fish.

I had them, and they got REALLY big ....from cute little 2-3" to 8" and ... growing at 6 months
... so I traded it back to Brian at Ocean Blue. Thanks Brian!
just look at this link on the BIG Giraffe catfish...
http://en.wikipedia.org/wiki/Giraffe_catfish
http://www.freshwatermadness.com/t2285-african-giraffe-catfish
http://aquaticpredators.com/forums/index.php/topic/21122-giraffe-catfish/
The larger variety are a lot more pushy and aggressive.
They tried to push my smaller FRT around during eating time and swallow up all the algae wafers. (LOL, my turtle held is own.)
So depending on the variety of giraffe fish you get, probably will be ok with the pleco but it may be how neighborly your red arowana is with other fish.
Hope this helps.