Something is wrong with my Giant Danio

[smmfish]

I noticed this evening when feeding the fish that my largest Giant Danio (about 5") cant close his mouth. It's like his jaw is broken.
My water params are : Ammonia - 0, Nitrate - 5, Nitrite - 0, Ph 7.0.
Temp on the tank is 78 degrees and they are in a 55 gallon, its only him and 3 other danios, and a couple of live bearers. They have plenty of room. Please help me with this mystery!!!!

 

[Lupin]

Appears to be a case of columnaris. Is the mouth white? Have a read with this thread by Guppy. Here's the one by Oddball.

 

[smmfish]

I'm afraid that is not it. For one, the tank does not have a bacterial overload, there are only 7 small fish in a 55 gallon tank. Also, the mouth is not white, he just can't close it. I do waterchanges once a week, as you can see from my water params I posted in the first post my water parameters are not off at all.
Also, one symptom is lethargic or inactive fish, my fish is still very much active.
I am stumped, I am going to add some aquarium salt and see if that helps, but I don't know.

 

[smmfish]

Here are a couple photos of my Giant Danio with the problem.
They are the best shots I could get of him, they are fast.

 

[guppy]

It could have indeed dislocated it's jaw, dislocations of this type are fairly common among fish. They can even do it yawning. Before doing anything try to look down it's throat for signs of swollen or destroyed gill tissue, if that is not present I suggest you (very gently try to reset the jaw by catching the fish and (using surgical gloves) gently press straight back at the hinge of the jaw with a round toothpick placed straight across both hinges of the mouth, do it very gently and only a 16th of an inch or so for a fish that size. I have never tried it with a fish so small. With larger fish you hold the fish in one hand and use your thumb and finger to first pull the lower jaw out then up a bit before letting go, it has worked for me with a LMB and a bluegill.

 

[smmfish]

Thanks Guppy!!!! I will attempt it in a few minutes. Thanks again!!!

 

[guppy]

I always figured that the fish was doomed unless I tried so I tried.

 

[smmfish]

Well, I tried and he didn't make it. He also started getting cloudy eyes, so I really don't know what the heck was wrong. But at least I tried to save him.
Thanks Guppy for the advice

 

[guppy]

Either the dislocation caused a bacterial infection or the bacterial infection caused a bacterial infection, bothare more damaging in a smaller fish. You did try. Without treatment a fish that cannot eat, dies. Trying to enable it to eat can work, and the fish lives, or not work, in which case it dies anyway.
Tough breaks guy.