Commet Got Beaten Up

[Shannon1993]

Hi everyone
 
My boyfriend and I went house sitting for a week and his parent checked up on our tank to do feeding ect..
When we got home today I sat down admiring the tank and I saw that 1 of our commets is badly beaten up.
It battling to use its 1 fin and its like bloody all over.. I don't know if is a sickness or if 1 of the other fish got hold of it.
 
I have 2 commets
1 pleco
1 rainbow shark
Couple of neons and guppies
and 2 glass fish
 
I don't know if it was maybe the rainbow shark or the glass fish and I have no idea what to do about my poor commet..
 
Someone please help
 
Thank you

 

[Munroco]

Do you have a spare tank or large container where you can isolate him and treat his injuries? I'd say the prime suspect would be your shark

 

[Ninjouzata]

Agreed with the above.
 
Can you get a picture of your comet? This might help tell if it's an injury from another fish or if there is something else going on.
 
Do you know what your water parameters are btw? And what size tank is this?
 
There are some issues with your stocking but definitely want to help your comet first.

 

[BaylorPerez]

the rainbow shark is a territorial bottom dweller, usually it can be aggressive but it can also not be aggressive, as they only really attack sick, dying, dead, or fish that go into its territory. 
 
Based on your post the Shark is the culprit. Due to its territorial nature, the fish may have gone to where it shouldnt have, causing the injurys you see currently. Their is a 25% chance that the fish will survive, based on my own experience, most fish my rainbows(before they died) attacked, didnt live more than 2 days