Can fishes spot a diseased companion?

[Wyld-Fyre]

I wonder, is it possible if fishes are intelligent enough to avoid a diseased companion?

I have heard that they can be ostracized (spelling), attacked, and perhaps some fishes even support each other(?)

Of course, being in an enclosed space can mean fishes cannot effectively escape from each other if the worse happens.

What have you noticed?

 

[Raechal]

Well when I added a pineapple sword that was thrown onto the street and badly heart into the 29 gallon where my dalmation molly was, she swam straight to the bottom and sat right next to the poor pineapple swordy all night long. When I woke up in the morning to find the pineapple swordy dead, the dalmation molly was in the exact same spot right next to her.

 

[Tokis-Phoenix]

Good question! it is somthing i have wondered about alot, i think it mainly depends on the type of fish and the desease.
A while back now i had a whitespot out break which affected the whole tank after a f.betta i bought brought it into the tank.
The neon tetras were the worst affected but still shoaled together regardless of the infected ones in the group; then again i don't realy regard neons to be the brightest of creatures and it is probably more of an instinct thing for them than anything else.
Amongst the other affected fish were the platys; i noticed as worsly affected ones soon dispatched themselves from the group and hung around the bottom away from the main groups. Wether this was because the healthy platys didn't want contact with the sick ones, or the sick ones were too weak to follow the main group i don't know.
On the other hand, my big plec seems to enjoy munching on its dead tank mates regardless of what they have died of although strangely has never suffered from any deseases at all in the 6months i have had him, despite eating numerous dead neons and a couple of white spot death victum platys. This also goes for a male betta i used to have who grew a taste for neons when i had the whitespot.
(in total i lost 2platys and 15neons from the whitespot).
....
On the other hand, my black m.mollie once had pop eye(thankfully had a full recovery) and during that time the other mollies in the tank still acted totally normally to him.

 

[Def]

It's perfectly possible, depends on the fish. There are plenty of marine fish that are facultive cleaners and will remove parasites/protozoans from other fish, so they must be able to see it. I think you'll find most home tanks are way too small to provide room for fish to avoid each other.

 

[Wyld-Fyre]

Thinking about it more so. I suppose it depends on whether they're a schooling or territorial fish.

The schooling ones, such as Tetra's, would stick together no matter what...To their detriment. And the territorial ones, such as Cichlids, would find solace in their own space.

Caused by bad food (I suspect), I had Dropsy a little while back in one of my Tiger Barbs, and the others, I think, left it alone, or could it be that it was too lethargic to be interested in schooling?

I think you're right Def, when you say marine fishes are able to spot parasitized fishes. So, in my assumption, fishes are also able to recognize diseased individuals.