SPS are STNing from base up! HELP...

[solar]

Lighter color on sps could be growth

 

[fraggingfish]

Sounds like an alk swing to me.

Phosban usually causts STN throughout the SPS, starvation. You'll also notice pale colors of corals.
Base STN or RTN is change in other parameters, most commonly ALK.

If you're doing a water change, a direct application in the display tank may cause STN as well.
The best method of water change would be slow and steady pace, or directly pour it into the first chamber of your sump to help dilute the new content.

 

[Stpatrick]

Sounds like an alk swing to me.

Phosban usually causts STN throughout the SPS, starvation. You'll also notice pale colors of corals.
Base STN or RTN is change in other parameters, most commonly ALK.

If you're doing a water change, a direct application in the display tank may cause STN as well.
The best method of water change would be slow and steady pace, or directly pour it into the first chamber of your sump to help dilute the new content.

I agree. It's not the tips. It's the whole top surface. Be it a branch or tip.

 

[fraggingfish]

Sometimes there's other unforeseen circumstances we are not able to understand.
Such as beneficial bacteria in the water column, a water change destroys a large amount of that population.
It is quickly repopulated a few days later, but a direct application may cause a shock for those corals.