I have noticed, since we found our mated pair, that at certain times of the day(ie 3pm-5pm), our mated male is most aggressive. The other 22hours all of our puffers hang out together and even eat together. It just seems like at that particular time everyday day for the last 2 weeks or so, he's crazy aggressive. Is this normal? Do they only get in 'heat' at certain times of the day? They have all been housed together since around May 09. Thanks in advance for any advice.

As far as I know, each "couple" will work out a breeding schedule that works for them; it's probably as long from the last mating as it takes the female to produce a new store of ripe eggs, so you may see it slow down as she gets elderly.