Where is the photo of your coral you are having problems with?

More information would help. Is it a new coral that is slowly getting darker brown? Did it suddenly get a brown spot one day? Is it an old coral that used to be yellow for years then went brown?

There is no special conditions to make a leather yellow, it either is or isn't. Often times a newly shipped one will appear more vibrant due to stress, and when you take it home and make it happy it will darken to its natural color. Or if it was a nice color for a long time and changed, something has upset it and you need to share test results to figure it out

Mine was marketed as a gold fiji however the only Sarcophyton I've personally seen that was 'yellower' was a newly imported artificially dyed specimen. I'd like to believe this practice is no longer done but I don't know for certain. Zooxanthella is brown. The pigment that coral produce as a 'sunscreen' is coloured and so the shadowed areas of the tissue of coral is typically less vibrant and more brown than the heavily exposed areas.

Anyways:
250W Phenix 14K MH DE in LumenMax
Bottom
30x and indirect
78F
1.025
Ca +400ppm
Alk 9dkh
Mg 1350ppm
PO4 and NO3 undetectable with hobby kits but slightly higher than I would like.

read
 

People are able to read but unable to comprehend.

again
 

Again able to read but not comprehend.

Have you tried positioning it higher or middle and noticed a difference ? Tried different lighting ? Have you noticed anything that makes the Toadstool either lighter or darker ? You have the yellow in the middle so there is no doubt what it is. But the polpys are a tan color almost a light brown.



I will give you some more info. on my TRUE VIBRANT yellow toadstool. I was at a store and saw the most white toadstool that I have even seen. There were about 4 of them. I inquired if they were bleached and was told no. I was told they had been in the store about a month and had remained that color. I took the coral home and was disappointed that after a few weeks the while polyps were darkening up.

In less then a month the WHITE toadstool became the most BEAUTIFUL VIVID yellow that I have ever seen in person and with my own eyes.

As the weeks went on I noticed the yellow browning slightly only to get darker as the days went by. I eventually started playing with lighting and position and was starting to get the tan color back. I sold my aquarium and livestock shortly after.

I have talked to the person that bought the toadstool and it never got that yellow back but only a tan color. He gave me a small frag but it just disintegrated after a few short days.

Yellow toadstools are not hardy what so ever and will die if you look at it the wrong way.


In your picture the darkest areas that was what I was getting back the tan color before I sold everything off.

I think it's pretty obvious the store you bought it from was misinformed or lied to you.

You saw it totally white in a store, brought it home, it got darker after some time, then after more time got even darker. That is a perfectly typical experience with a bleached coral, white in store>>yellow later at home>>brown later on.

The picture posted is what you can expect from a fiji yellow toadstool, if you see them brighter it is because they are stressed out and either in the process of bleaching or recovering from bleaching. You cant force them to stay that color, they will always drift one direction or the other depending on if they are happy or not. It is also possible you've seen dyed ones, the local coral collectors used to dye them yellow so people would buy all the brown ones when they ran out of nice ones to find.

Your expectations of a leather coral are too high. There is no such thing as a permanently fluorescent yellow toadstool.

hmmmmmmmmm
 

White to yellow is normal ? So you are saying there are no true yellow leathers ? What I had was not a bleached looking yellow but pure true yellow.

There are yellow leathers, just not "lemon" yellow that you might be expecting. I found some images to help explain:

Bleached out yellow leather, what you'd see in a store
https://i.imgur.com/vtP0VRk.jpg

Transitioning to normal color, but looks really nice and bright yellow
https://i.imgur.com/Oy1uGqW.jpg

Natural color that you should expect in the end, right on the mariculture racks in the ocean
https://i.imgur.com/Ha59L5t.jpg

There will be slightly nicer ones, and blue leds or actinic bulbs MAY help the yellow pop a bit, but they should all end up about the same

Pictures
 

The pictures helped immensely. So, no one is able to maintain that nice bright yellow ? They ALL eventually turn to the mustard yellow color ?