Sudden Betta Aggression

[New2Betas]

Master Betta has been in a cycled 10 gallon with 4 corys and 3 ghost shrimp for over 2 months now and has never had a problem. Now all of a sudden today he is chasing the corys, flaring, and looks like he has been tail biting. Nothing has changed at all. I have him in a breeder box in the tank right now so he does not harm the other fish. Any help would be greatly appreciated.

[xxabc]

I'm not surprised honestly. I've heard from time to time about tankmates with bettas. Sure at first it may work (although even then, there may be complications), but it's like a time bomb - who knows how long it'll last? See if it will subside in time. If not, you need to take him completely out. He's suddenly decided he won't take it anymore.

I feel like bettas are more territorial fish, so I try to stay away from other fish (my own opinion).

[Mister Sparkle]

do what you think is best. Some bettas just won't make good neighbors. The only reason I'm responding to this thread is because I think "master betta" is a great name!

[New2Betas]

I had him out of the tank for about 7 hours, put him back in and he's back to his happy self. Must be Betta PMS.

[Tinman23]

You can never know with bettas, one day their fine, the other they're not. I had the same problem, and eventually after ended up having to put him in a separate tank for good. But good hear your fish seemed to work out their differences!

[vaygirl]

Tango's started chasing the corys a lot more recently. He doesn't wound them or bite them, he just chases for maybe 2-5 seconds and then goes about his business. The corys seem to know the difference too. I've seen them all laying around together and Tango is among them on the gravel. I've seen him cruise right up to them and they don't flinch. But sometimes it's like watching Benny Hill and the corys seem to know when to take off.

Watch for wounds and such. I check my corys daily just to make sure nothing hinky's going on when I'm not watching.