Randall Goby Dorsal Fin

[holy carp]

I added a Randall Goby to my tank on 8/19, and he immediately found my pistol shrimp and moved in

 

Here he was on 8/21

 

Then a few days ago I noticed a small notch in his dorsal fin.  At first I thought maybe he snagged it a little bit in his burrow, but it was tiny. 

Yesterday I noticed it was a little larger, and looked like it was tearing.  I wasn't sure if this was from when he flexes his fin up.

This evening you can see the notch in this photo.

 

 

And I'm heading out of town for a week in the morning, so I'm wondering if there's anything I can/should do before I leave.

 

Also, you can see a change in the black spot...

[Tamberav]

Hm, I would be concerned of some sort of infection or parasite, flukes can sometimes tatter fins.

 

In your first video, if you look closely, his tail is tattered too. If you have other fish, you can assume they are infected too but depending on what it is, they may not get as sick.

 

I have used PraziPro in the DT before but it has its own risks and I wouldn't recommend it if you are leaving. I am not entirely sure it is flukes but something is amiss. 

 

 

[mitten_reef]

could be a bite mark?  Were the clowns behaving ok around the newcomer? Were they showing any territorial aggression, they can be really mean if they want to. I had a cherub angel beaten up so bad by my established two clowns, I had to remove him.

[holy carp]

As I looked at it more, I began to wonder if he might be 'burning' his fin on the war coral as he backs in and hangs out at the 'door'.  They switch their burrow entrances around a bit, but the one where pictured is definitely the primary entryway 90% of the time.  And the rest of the time is split between the other side of the war coral (possibly same condition) and the two holes at the bottom of the rock to the right of the war coral.  Their burrow must tunnel all the way through.

 

There is also a clownfish and a dottyback in the tank, but they show no signs of any damage.  They both live on the other end of the tank, so I don't believe there's been any interaction.  The main reason I don't think it's a bite mark is that it has increased over the last 2-3 days.  I wouldn't think he'd get bitten in the same spot repeatedly.

[holy carp]

Oh, and the tail was tattered when I got him.  That must have happened in the display at the lfs...

[hooligan_78]

Did you get him from MA?

[holy carp]

Yes, from Manhattan Aquariums.

[hooligan_78]

I just picked me up a pair of flame dartfish.