Problems with Acropora corals

[Reef_do_piza]

Did you buy these Acros with color? If so, give me an approximate timeline of when they lost their color to this brown look. Rapidly losing their pigmentation versus slowly browning would be very helpful. Also, I know you mentioned you have two Radion G4s, but have you measured the PAR these Acros are receiving? IME, SPS that start to lose their color typically happens when they aren't getting enough light and/or nutrients from the tank. Since you have decent nutrient numbers, I want to explore how much light they are getting. The salinity changing is not the reason why they went brown.

Something to consider - an ICP test because then you can start to document what your corals looked like at the given conditions they are living in.

Yes, they were colorful when I bought them. The ones that arrived via air freight were brown, but the others—which I picked up at the store—were colorful at first; they later turned brown and lost their color.
I haven’t measured the PAR yet, but I will do so this week.
I am currently awaiting the ICP test results.

 

[Reef_do_piza]

I am no acro expert but I see some PE on the acros which means they are not completely unhappy.
The parameters seem fine.
The side that not facing the light will usually look whitish with lights off.

Also I assume it’s a well established tank.
You also dipped your corals before adding.

Add aminos as per dosage instructions.

Borrow a par meter and check light levels.

I want to add amino acids

 

[Reef_do_piza]

Agreed with the posts above that the parameters look good and form the picture it seems the tank is well-maintained overall. I also would not make any drastic changes if the other coral are doing okay. First issue I would try to address is reducing the aptasia population. Very annoying pest so I hope the filefish works for you!

thanks, appreciate it