Help with Hippo

Ugh. I really hate having to post here. But here's my dilemma: My hippo has a injured pectoral (side) fin. I really can't figure out what happened. Everyone in the tank gets along, and the rock structure didn't move/collapse or anything. The tang was fine when I went lights out last night, but I noticed it first thin with lights on this morning. So, do these types of injuries heal? She is hiding more, but she does come out and is eating.
More info via Mission's sticky:

PARAMETERS (important)
Temperature: 78-80
PH: 8.3
Ammonia: 0
Nitrite: 0
Nitrate: 0
Salinity: 1.026
dKH/KH/Alkalinity: 12.1
Magnesium: 1550
Calcium: 480
Phosphate: .2

Tank size? 40 gallon
Estimated total system? ~40 gallon

Reef, fish only or, freshwater?
Reef
Current inhabitants? What and how many?
Clean up crew?
2 damsel's, 2 clowns, blenny, mandarin, hippo, 2 hermits, 3 turbo's
How long has your tank been set-up?
7-8 months
Substrate.
Type? fine sand
Depth? ~2"

Live rock? yep
How much?80-90lbs
Did you recently add some?no

Filtration.
Type? mechanical hob and skimmer
Protein skimmer?octopus bh-100F
Do you wet or dry skim? dry
Maintenance schedule for filtration? once a month on filter, whenever cup needs cleaning on skimmer


Lighting.
Lighting type? MH/T5 combo
Age of bulbs? ~4 months

Feeding
What? mix of frozen
How much? not much
How often? every other day

Water change schedule.
How much? 20%
How often? every 2 weeks
What salt brand? Reef Crystals
Water source? Treated Tap

Additives/supplements used? Ca, mg, and alk supplements only

Do you have a ground probe?Yes
What kind of flow does your tank have? 2x koralia 1's in addition to skimmer and filter. 36X turnover rate

 

So the fin is damaged, but is the fish struggling to swim? I have had a clown with serious injuries and couldn't even swim. I QT'd him so that he would get food and appropriate care. I don't think you need to QT this fish as i'm pretty sure he can hold his own against anything in that tank. If he's eating I would ensure good water quality so that it doesn't get infected. I don't think you can put a splint on a fish , maybe someone else has some more experience with treating physical injuries. Sorry for the injury, but hopefully it will recover fully.

 

No, it seems to be getting around OK. Since its the pectoral fin, it does have a little trouble staying stable in say, the direct flow of a powerhead. But other than that its doing ok. It comes out and swims around on its on choice, and comes right up to the surface with the other fish if I have the food bowl And yeah, I'm sure the other fish aren't the problem. The best I can figure is that it somehow hurt itself overnight hiding in the rocks (it likes to sleep DEEP in the rocks), as I have a hard time believing another fish did it in the middle of the night.

 

OK. I know it has the water quality and food it needs. I don't have a CBS, however, just a couple hermits and a skunk shrimp. I guess it could have been a hermit, but I seriously doubt even that.
And I should have said, as for the fin, it seems like its almost a bone injury. It can barely move the fin at all; but the fin structure itself is intact. Mean anything different?

 

Not a bone injury, there aren't any bones there to break. They have these things called "thin bones" i believe, but they're more like cartilage than bone. They're quite flexible, but it could have done some damage at the base if he sleeps deep in the rock.

 

That's what I am worried about. It has spent most of today hiding. It came out and ate during feeding then hung around outside for an hour or so after wards. Fin didn't really look any better though. Its tore up, kinda whitish, and seems to be completely immobile. :-/ I think I am going to go lights out early tonight and probably leave them off till a little later tomorrow, maybe just to give a little extra stress free rest.

 

Q: Has your fish been watching "Jack-A$$"? LOL
But seriously, I've seen some pretty mean blue legged hermit crabs, so it could have been a hermit that attacked the tang while it slept. I'd add veggies/seaweed to the mix of frozen food that you're feeding. Keep an eye on the injury, and pay close attention to signs of infection. If the injury becomes infected, then you'll need to worry more and treat for the infection.
Good Luck.

 

LOL. Not that I am aware of. Last night it was geeky sci-fi shows on the TV
Frozen algae/veggies are always part of the food mix, and I tie down broccoli and nori on a regular basis. I don't have any blue leggers, they are red/scarlets. I guess its a possibility, I would just think something as mobile as a tang would be able to get away fast enough before one would cause any real damage. I don't think its infected; it is white, but I think thats more of the actual injury. Its not "fuzzy" or anything like that, nor is it spreading

 

I don't think it would have been a crab - I don't think they're strong enough to cause it to be completely immobile.