just because a aro can grow to 36inch doesnt mean it will need that space to turn around aros are very flexable and a 3ft silver or black aro could turn around in 30inch easy with space to spare
jardini and asian aros are not as flexable as silver or black aro due to the fact that they have bigger scales
lenght is the most important and should be about double the adult size of the aro MIN
the the next important thing is width a 4ft silver or black aro chould turn around in 24inc wide but to give a bit more room so i would say 30inch MIN width
the last important thing is depth but if you want to keep any mid water tank mates then 24inch is the MIN depth
ooops sorry but i do know how big silver and black aros get
oh look i used to keep a 27inch Black aro in a 72inch LONG x 24inch wide tank and that had no trouble turning around for thr 7yrs he was kept in that tank
but the tank was to small but only in lenght