5 Gallon Tank Only one of my Bettas have Black gills

My half moon Betta (white) has black gills where as my veiltail Betta (red)
doesn't. was told that black gills means terrible living conditions but my red one doesn't have them (.they are kept in the same 5gal tank with a divider) My white has had them since I've bought them from the pet store (just over three weeks ago) I dunno if this is normal for half moons or if I'm doing something wrong. please let me know (it's possible he could change to black but I just wanted other opinions just to make sure)

 

Unfortunately, I can't speak for the halfmoon theory. The only halfmoon I've ever had was completely black... so his gills were black, too.

However, what are your water parameters? It's good to check there first. Most bettas are not in good living conditions at the store. I've only ever been to one that actually keeps them in barracks with filters, but it sadly closed during the height of the pandemic last year. It's possible that it's residual. Also, many bettas don't present their full colors until they're full grown, so he may end up changing color a bit as he matures over the next few months. He could end up with black on him.

 

Last time I checked his parameters were 7.1 or 7.2 at my pet store (pet smart) they were kept in little tubs they looked like this (not my picture)

 

Do you have the nitrite, nitrate, and ammonia readings?

 

Yeah nitrite level was 0.5
Nitrate was 19
And ammonia 0.024

 

It could be that your nitrite is high. Nitrite and ammonia levels should be at 0 ppm, so I would do a 50% water change ASAP and then a 25-50% water change any time your nitrites go above .25 ppm. What conditioner do you use? Seachem Prime is a good one to use while nitrites and ammonia are high to neutralize them so they don't hurt the fish.

 

I just did a water change 1 hour so they should be good and I use aqueon water conditioner