KJAK wrote:
I was thinkn of a 5 or 6 ft long tank for them
To quote a famous film starring a very big fish
you're gonna need a bigger tank
A 5 or six for tank is not going to be much bigger than 125 gallons if it is a standard size. Arrowana can easily reach 2ft in captivity, the other fish you are talking about will reach in excess of 12 inches by themselves. I really wouldn't be thinking about anything less than 200 gallons if you want to give them plenty of room. However, finding a tank of this exact size might not be that easy unless you make it yourself, many of them come in standard sizes, aquariums big than 200 gallons are not really that common off the shelf.