Had 5 originally to prevent fighting , but now reduced to 3 . Nothing much happened supposed they can go up to 9-10" , my biggest now is 6" or so they dun grow as fast. My Arowana mostly ignore them except when they stealing his food, but as usual avoid anything that can fit its mouth.
I have a few other plecos inside, as for BN , the fairy fin L144 i kept from 2.5" , is being ignored totally also. Thou have DW and sound hiding spots but when meal times it crawls all the way up to the top of the tank to help himself with the aro pellets.
Yah, i should think its fine .That's pretty much what i did to my tank.
They will be chasing around themselves abit, should be nothing serious once the order is established things will pretty much settle down.
But as always there will be some risk with a smaller BN, abit of luck sometimes depending on the temperament of the Arowana.