Fish brain damage?

I may have just witnessed an accidental fish suicide. I went to clean up the stuff from my old QT (I've upgraded from plastic container to glass tank), needed some better light so I reached to turn my desk lamp on. The tank lights have been off for a few hours (evening/night) but the room has been dimly light the whole time. My desk is close to my 105L planted tank and I think my arm reaching spooked a sleepy fish. The fish darted into the glass, making an audible clink noise. It went still, when it crashed into the glass (coincidentally at the water surface, it did not float up or move.) Still breathing/gills moving. It happened about 6-8 minutes ago, but he hasn't moved apart from breathing.
Have I accidentally caused this fish to kill itself or could it just be shocked?
Sad timing, I had to euthanize one of the group a week ago

Good update: I just went to see if the fish had moved and it has! I don't see it, but the tank is in the dark. Meaning I don't see any of the fish.
Hopefully nothing fatal

Give it 24 hours and see what happens. Hopefully it's just a concussion like @emeraldking had from his fight with a murderous rampaging tree that mugged him in the street

Colin_T said:

Give it 24 hours and see what happens. Hopefully it's just a concussion

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I hope so!! I'll put an update on here tomorrow

rebe said:

I hope so!! I'll put an update on here tomorrow

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Yes, give it some time... Also a fish needs time to recover.

I used to keep a pair of discus in a 25 gal. tank for breeding. I got lots of eggs that were never viable. I tried changing the male as I thought it might be sterile. I ended up with 2 females. And then I lost one. I gave up on spawning but kept the last discus. The tank was in a bathroom and one day walking into it I must have spooked the discus as it bolted into the side glass. The sound of that collision was pretty loud.

The result was that the fish immediately developed balance issues. It went nose down. It could fight its way back into a normal position, but could not hold it and would quickly go back to nose down. I hoped it might be swim bladder issues which might go away, but I soon began to think it had damaged its brain as the cause of the balance issues.

I will not euthanize a fish unless I am convinced it is suffering. The discus could eat off the bare bottom in the tank and it was alone there, so would not be picked on. It lived in that tank for about another 9 months before it passed one night.

Very early on as a fish keeper I got a pair of dwarf gourami (Trichogaster lalius). The male built a bubble nest and they spawned. After that the female becomes persona non grata and he will not tolerate her. This was in a planted community tank which was on a stand in the opposite corner of the room as the door. As I was walking into the room one day the male had just gone after the female and she bolted hard into the glass. I could hear it from across the room. She was dead not long after.

This is one of the potential downsides to keeping fish in glass boxes. It should not take very long for you to determine if there is more than any temporary damage to your fish.

So does he look okay now?

GaryE said:

So does he look okay now?

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I don't see any odd behaviour in the group. I wasn't sure if I was counting 12 or all 13, and the lights off now for the evening. I think the fish is either fine or "missing"