That exactly what I've done, and I have black card around the tank as well so that might calm them.
I left them for a few minutes to calm down but it is up to the individual fish at the end of the day.
The young Jacob for instance was in full flare mode in his tank but had lost a lot by the time I shot him.
I almost thought about putting another peacock in an adjacent tank to get them to flare-too much work
A lot of them want to scoot around the bare bottom. Thought about putting in substrate but didn't want anything that might murk up the water.
I was shooting at about F16 so was getting pretty good depth, but was shooting with macro so maybe a lens that I can pull beck a bit would be good, but I did want to get 'into' the fish.
The thing I want the most is to get true colours as when in tank under tank light it is hard to shoot 100 iso so they can tend to contrast up and over saturate at higher speeds, and hard to pick out the eyes.
In tank shot with tank lights
in photo tank- although over bright from below from whit poly under tank
So a bit of fine tuning needed.
You're right about the painted black not given an even finish Barrie, but i dont have a problem in cleaning it up 'post'
The 3rd fish is a Sajica young male- as Ryan has rightly noted in his guess game