how pink is good for me otos' underside?

The gill area should be pink, sometimes after the oto has been swimming it goes a bit darker but it shouldn't be dark red. I just took a photo of my Oto to show you.

Oto 1.JPG
 
ok, so I've been watching my otos for a week now, checking on their pink status. 2 of them seem similarly slightly pink, where the 3rd is looking darker, and it seems like the pink extends further... and he sometimes seems to act a little eratic. my amonia level is, and has been 0 for weeks... could my little guy have some other problem?
 
If they're active and eating I wouldn't worry about it.
 
Yeah, my ottos have varying levels of color to their pinkness. Mostly just watch and if you notice anything out of the ordinary, run a water test, and maybe an extra unscheduled WC just 'cause (be surprised how much that helps sometimes)
 
trying not to worry, but it really seems like this one guy is getting redder. the reddness seems to reach around his mouth, and there is a hint of redness on the top of his nose too. I know the picture isn't the best, but you can see the comparison between two of them...

I really don't want to lose him.

KICX1908.JPG
 
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