Dependant on how many fry and ow long you want to grow them out to, the will have to be pretty big before indroducd with angels. You will need a fairly large growout tank for the fry with good filration in this case, so as mentioned all depends on the amount and how long you plan to keep them in there and how big they will be when removed?.... i tank for the BN's alone would be better. group of 3 adults and time to have the fry grow to be moved i would say 3 foot tank...... just for the fry alone you MAY get away with 2 foot but again dependant on what i mentioned above in relation to size and amount.