I am doing mine with research 
Flame Angels being the anal fin being rounded for female and pointed for male. Both flames are small. One of the flames has a very pointed anal fin while the other is more rounded. However, I do feel that the "female" might have been turning to a male when I got her. IMO, it seems to be recessing to a more rounded anal fin like various websites have written would happen.
Six Line Wrasse: Bigger wrasse being assumed is a male with the colors being extremely bright and livid and then putting a smaller wrasse with it hoping that it's a female since what I hear, six line wrasse start of as females.
Disclaimer (aka side note): Both sets of fish are being observed for aggressiveness and any one that shows signs that there might be an issue, they are pulled IMMEDIATELY. So, please don't flame me for trying this out and the approach. I care for these fish and will make sure they are treated well and nothing happens. I am just trying to express what I am doing and my reasoning behind this. Having a pair is not needed but trying this does not harm anything if monitored correctly which I feel is happening here.
Flame Angels being the anal fin being rounded for female and pointed for male. Both flames are small. One of the flames has a very pointed anal fin while the other is more rounded. However, I do feel that the "female" might have been turning to a male when I got her. IMO, it seems to be recessing to a more rounded anal fin like various websites have written would happen.
Six Line Wrasse: Bigger wrasse being assumed is a male with the colors being extremely bright and livid and then putting a smaller wrasse with it hoping that it's a female since what I hear, six line wrasse start of as females.
Disclaimer (aka side note): Both sets of fish are being observed for aggressiveness and any one that shows signs that there might be an issue, they are pulled IMMEDIATELY. So, please don't flame me for trying this out and the approach. I care for these fish and will make sure they are treated well and nothing happens. I am just trying to express what I am doing and my reasoning behind this. Having a pair is not needed but trying this does not harm anything if monitored correctly which I feel is happening here.



