your tank/filter should cycled already by now if done right
sounds like your arowana is advance stress state or possibly fin rot (i cant tell without pic), whats the temp on the tank?
jumpy/skittish is normal for arowana that size not eating is not for that size.
the fat goldfish might not picking on him but it might freak due to the size and goldfish behavioral? means the aro in extreme defense mode all the time
The temperature is currently at 81*F and yes maybe the arowana is in defense mode. the gold fish likes to suck the poop out of the arowanas butt for some reason....
I'll try to get a picture up too.
