yeh ure pond is fine for life. pacus might need a deeper pond because they grow quite high as they do long. perhaps 3 feet deep. red tails dont swim all that much if they r full. ure 12 foot pond shud be fine. pacus, TSN and RTCS live together all the time. the problem comes with size. if they are all similar in size then it shud work out fine. no promises.....there have been too many disasters to gurantee anything.