Yellowhead Sleeper Gobies fighting

[magnetar68]

I bought a pair of yellowhead sleeper gobies (Valenciennea strigata) about 6 months ago. They were small (about 2.5-3") when I got them. They have been staying together constantly and living in the same little hole. At first they would only eat frozen foods, but now they eat everything, eat flake foods. When I first got them, they were about the same size, but now one is somewhat larger than the other. This week, I noticed the bigger one going after the smaller one and forcing it back into its hole whenever it comes out. Anyone have experience here? My concern is that the smaller one is having a hard time getting food as the larger one drives it back into its cave when it comes out to eat.

 

[magnetar68]

It's been a few more days and the larger is still agressive towards the smaller. Here is a video of the aggression:

http://youtu.be/yl6DLK-eC70

Here is a video from January where they are pals (first part of the video):

http://youtu.be/BTDtg9JdJ-k