i think you're looking at this is the wrong way, These are fish which will inevitably out grow a 5ft tank in no time. The arrowana is large and prime nipping material. The GATF grow to 30" 100lbs with razor teeth, they are best kept in a group and will not thrive in a 5ft. The 1st video you posted, yes the fish are not killing each other, but the space they have is comparable to a goldfish in a bowl and in not too short a time, there will probably be some injuries inflicted. Do not buy fish which are not designed to live together.... and especially not when the risk of death is higher than that of happy living!