Well, I live in Thailand, had an Arapaima swimming into our factory during the great floods of 2011/12..
With water withdrawing, he got lucky in a large storm drain where we found him...He was then about 90cm...
We built a pond for him and he is now close to 2 Meters!!!
Coming back to the OP's question.. Way To Small !!
Mr. T's pond is 10 x 6 x 1.20 meters.. And with his current length, he's still very comfortable, but he keeps on putting weight and length.
And to confirm HungDang's statement, yes, there's plenty of breeding and plenty of fishing lakes where you can try your luck on fishing Arapaima, Pacu, Barramundi, Red Tails, Gars..etc..
The biggest Arapaima caught to date was 10 Feet and estimated at about 450 pounds!
http://www.fishthailand.co.uk/catch_report_andy_harman.html
With lots of pictures. The lake he caught it is world famous.. Been there a couple of times Catfish fishing. Largest I've had was about 25 Pounds. Can only imagine how this guy has been struggling.
Cheers,
Luc