Problem with sleeper gobies

[RoTTen2TheCore]

Ive had a pair of sleeper gobies for about 3 months now and they have gotten along great, always following each other and so on, until yesterday when i noticed the larger one one was bitting the others mouth and was thrashing it around!!! So i knocked on the glass and it let go. Today i came home and saw that the larger one was swimming alone and thought that the other was probably dead but after searching my tank, i found its been hiding behind my filter. Why would they all of a sudden not get along? When i bought them they werent juveniles so i find it strange that the problem would be they are both male.

Any idea why? and what i should do?

 

[Blown 346]

Sounds like territory issues. The only thting you can is watch them closely. The only other thing would be to move some rock around after the lights go out. This will confuse them and they will have to get new territory.