Harlequins Missing Eyes

[daveg6529]

When I checked my tank this morning I noticed that one of my Harlequin Rasboras was missing an eye. This caused me to look closer at my shoal, I found two others with one eye missing. None of them appear distressed or injured in any other way.
I have not seen any fish being aggressive towards them but one of my penguin tetras does chase the other fish in the tank occasionally (never actually catching any).
 
Has anyone heard of Penguin tetras attacking Rasboras?
 
Tank 260ltr.
Temp 25 degrees C
Ammonia Minimal less than 0.25
Nitrite 0
Nitrate 40
PH 7.6
 
Tank mates
1 - Betta
10 - Penguin Tetras
10 - Neon Tetras
8 - Glowlight Tetras
6 - Peppered Corys
8 - Harlequin Rasboras
6 - Glass Catfish
6 - Assassin snails.
 
Filter Aquamanta 300
 
Any ideas?
 
 

 

[FishGuy123]

Hmmm maybe is your betta aggressive? does he ever flare at the rasboras? I know my betta is extremely aggressive and territorial. 

 

[techen]

I second the betta, More than likely but harlequins are quick so am not entirely sure.

 

[daveg6529]

I know that this sounds sad but I spent over an hour today watching the tank. Initially I was trying to photograph the fish but I took the opportunity to watch the Betta. No flaring, and he seems to peacefully patrol midtank away from the water flow. He does not appear aggressive towards any of the other fish.
Still it was only an hour so I will keep observing on and off.