it will depend on what kind of clowns you get...the maroons get a large size, but the smaller orange ones do not get too big...w/ 4 yellow tails, if they all live, they may not exibit too much agression so long as are not adding new fish after them...I would go w/ the yelloe tang as it tends to be more hardy and sociable compared to pygmy angels like a flame, but it does get much larger than flame angel...you will need to add some kind of rock in your tank preferably Live Rock...as the damsles like having place to hide or stake out turf & tangs need something to graze on as well as to hide when sleeping...don't freak out when sleep time comes or time just after lights go on & it develops a white stipe when darkish area around it...also I would suggest at least 2 power heads for good water circulation