well after reading every page of this fiasco i must admit i'm torn for two reasons.
1) Bderick67 i agree with what you are saying, you can let an arowana survive in a smaller tank but will it thrive? In this case i totally agree with you.
2) TheCanuck you also bring up some very great points although not very graciously, what you are saying is true. again it comes down to the point of will it thrive?
we can sit here and argue our personal opinions till the cows come home but to you OP i say that do what you feel is comfortable and responsible. Personally i could never keep a 30" fish in a 48" tank or a tank with a width of 18" now i am a little hypocritical right now as I currently have four asian aros in a standard 180g. they are all around 12". But once the grow larger i'm going to upgrade to a 10'x4'x4' tank why? because i want my fish to thrive. I understand that yes you can keep the water clean in a smaller tank and the fish will do ok. My water turns over 8.5x per hour and i do a 40% WC a week but i would never keep my fish in this tank for life? NEVER! Sure they will show good color and perhaps even live a long time BUT i think that they deserve a larger tank because i want them to be happy and comfortable.
OP i understand where you are coming from. large tanks can be expensive and DIY tanks can be a very daunting task. but is all comes down to what you believe personally. IF you think that you can keep an aro like they do in japan then please do, i wouldnt judge you if you did. Why? because if you think that that is the responsible way to keep your fish then i can respect that. but i think that being the care giver i would ask you to consider your choice carefully. Although i too have seen aros in tanks i thought too small and would never do myself i also must consider the other perspective. If that person loves and cares for HIS pet and it brings him joy then all the power to him. BUT i would definitely ask him that if he appreciates it that much, is his way adequate for the fish?
I know i am somewhat contradicting myself but this is the nature of the beast. I'm sure many of us dream of having even larger fish in tanks in our homes and although it may not be within our means it does not mean that we still dont want it or are selfish enough to keep it in something less than adequate. At this point i must say if you appreciate your pet would you not want nothing but the best for it? even if that means its not what you can provide?