Agree with all the guys are saying above.
IMHO, 500 gal is a minimum size for a 2.5'-3' arowana. But as stated just above, if you are inexperienced, rehoming and upgrading (even if you are able to do it financially and room-wise) can prove dangerous.
Please, don't feed your arowana only shrimp. It will cause it to develop a vitamin B1 deficiency, wither, and die. (Read up on thiaminase.)
The diet better be diverse. Pellets and whole frozen-thawed fish would be the staples and crustaceans like shrimp, insects would be good as treats.
Our silver aros in 4500 gal:
https://www.monsterfishkeepers.com/forums/threads/my-silver-arowana-in-4500-gal.688112/#post-7755675