It's not really a good idea to have more than one pair of clowns in a tank, no matter the size pretty much. I had the most mellow of all clowns, oscellaris ones and two pairs could not live in a 6 foot 125g tank without killing each other. The orange pair nearly killed my B&W pair in a single day. They were fine for maybe a month or two tops and then one day the orange guys decided to attack almost to the death the other pair. It was brutal to watch but luckily I had another tank to put the beaten up pair into.
Some people "might" have success but I think the majority of people trying it find it not to work.
125g Reef Yellow,Tomini & Blue Tangs,Watchman Goby, Squareback Anthias,
60g Rimless Reef- B&W clowns,citron goby, mandarin, scooter,Barnacle blenny,firefish
125g Malawi Cichlid
90GFOWLR Red & sixline wrasses,Flame Hawk,Squirrelfish,Engineer Goby,Coral Hogfish