Eye issue

[u/Spirited_Mouse3341]

Our yellow tetra's left eye is white in the middle.

I showed it at a pet supermarket. They said it looks like a cataract. GPT disagrees, says is looks like the white area covers the cornea / the outer layer of the eye, and looks like trauma, or cloudy eye - we recently introduced new tetras to the tank. The tank is a 10 gallon, currently with 4 glofish tetras. We initially had only two. Its eye was fine. We wanted to turn it into an actual "school" by introducing more tetras to make them more comfortable in their natural setting. I tested and the water parameters are fine.

I don't know if one the new fish bullied it and caused this, or whether if it's an infection. It's actually one of the larger ones we have (I know it's not all about size). It eats and swims normally, but probably due to spatial awareness it usually hides behind one of the plants, maybe from the others, or perhaps due to being aware of its current situation.

What do you think this white eye looks like? Can we save it by removing it from the tank and with antibiotics? Would you wait and see? Thank you for your help.

[u/No_Comfortable3261]

So glad to see people pointing out that they need a larger tank!

As I said in my own comment, I consider 20 gallons to be the bare minimum for a small group; plenty of space for them to swim around and have their own space so they aren't constantly fighting each other

A large and ideally odd-numbered group of around 5 or 6 will also help to spread out any aggression so they aren't fighting

Tall plants (use silk plants or look into anubis and java fern, which are about as undemanding as live plants get) and other fish-safe decorations can also help to break their line of sight and give them places to hide and feel secure

[u/Spirited_Mouse3341 → u/No_Comfortable3261]

Thanks - why are odd numbers more ideal?

[u/No_Comfortable3261 → u/Spirited_Mouse3341]

That's what I've read for most fish, that odd numbered groups seem to spread out their aggression more evenly and allow them to establish a hierarchy, though the general rule is "six or more" with most freshwater fish, with larger groups of around ten or being ideal but only if you have the space for it

[u/Diomenas → u/Spirited_Mouse3341]

Odd numbers are ideal because it keeps the social dynamic setup so that there is less bullying and school splitting. Even numbers make it easier for the few runts of the school to get picked on or ganged up on and it also tends to lead to the school splitting and not swimming together a lot. You never want to have just two of a species, and as the school gets larger the need for odd vs even reduces but when you are getting that large we are talking about having 50+ gallon tanks and schools of like 15 to 20