PH: 9. Corals closing

Bbio

Community Member
View Badges
Joined
Jun 20, 2025
Messages
93
Reaction score
60
Location
United States
Rating - 0%
0   0   0
Half of my corals have closed. Everything has looked fine parameter wise for months and over the past few weeks, things are closing and I finally got a PH meter and my pH is 9!!!

Tank is 150g 5 months old.


My RODI water is reading 9 also and my tap water is reading 8.3.


20260407_214107_81B3D367-C3D2-45A8-884C-DAC391FF9638.png

I have been having bottoming out nitrates and phosphates and lowering dKH so I’ve been dosing neonitro, neophos, and tropic marin carbo calcium.
 

That Crusso Kid

10K Club member
View Badges
Joined
Oct 21, 2018
Messages
15,176
Reaction score
77,402
Location
SW, FL, USA
Rating - 0%
0   0   0
Half of my corals have closed. Everything has looked fine parameter wise for months and over the past few weeks, things are closing and I finally got a PH meter and my pH is 9!!!

Tank is 150g 5 months old.


My RODI water is reading 9 also and my tap water is reading 8.3.


20260407_214107_81B3D367-C3D2-45A8-884C-DAC391FF9638.png

I have been having bottoming out nitrates and phosphates and lowering dKH so I’ve been dosing neonitro, neophos, and tropic marin carbo calcium.
If your RODI water is measuring a pH of 9 then it is time to change your resin.
 

ReneReef

Active Member
View Badges
Joined
Oct 9, 2018
Messages
335
Reaction score
391
Location
The Netherlands
Rating - 0%
0   0   0
How do you measure pH?
When in the light cycle do you measure?

A pH of 9 while dosing nothing that increases it is very unlikely.
 

That Crusso Kid

10K Club member
View Badges
Joined
Oct 21, 2018
Messages
15,176
Reaction score
77,402
Location
SW, FL, USA
Rating - 0%
0   0   0
How do you measure pH?
When in the light cycle do you measure?

A pH of 9 while dosing nothing that increases it is very unlikely.
I'm not so sure I follow you, but, like I said, if the pH of the water coming out of your RODI is 9, then you need to change your DI resin.
 

ReneReef

Active Member
View Badges
Joined
Oct 9, 2018
Messages
335
Reaction score
391
Location
The Netherlands
Rating - 0%
0   0   0
I'm not so sure I follow you, but, like I said, if the pH of the water coming out of your RODI is 9, then you need to change your DI resin.
Luckily you don't need to follow me, as I was responding to the OP's opening post.
So, you'll have to wait how this topic evolves and see if you can catch up at some point. Good luck.
 

That Crusso Kid

10K Club member
View Badges
Joined
Oct 21, 2018
Messages
15,176
Reaction score
77,402
Location
SW, FL, USA
Rating - 0%
0   0   0
Luckily you don't need to follow me, as I was responding to the OP's opening post.
So, you'll have to wait how this topic evolves and see if you can catch up at some point. Good luck.
Good catch! I thought I was replying to the OP, hence the confusion.

And good luck to you too!
 

Fish Fan

Master of Disaster
View Badges
Joined
Dec 8, 2017
Messages
13,116
Reaction score
34,175
Location
461 Ocean Boulevard
Rating - 100%
6   0   0
Last edited:

mcarroll

10K Club member
View Badges
Joined
Jan 8, 2012
Messages
15,217
Reaction score
8,978
Location
Virginia
Rating - 0%
0   0   0
Half of my corals have closed. Everything has looked fine parameter wise for months and over the past few weeks, things are closing and I finally got a PH meter and my pH is 9!!!

Tank is 150g 5 months old.
So tank is brand new.
My RODI water is reading 9 also and my tap water is reading 8.3.


20260407_214107_81B3D367-C3D2-45A8-884C-DAC391FF9638.png

I have been having bottoming out nitrates and phosphates and lowering dKH so I’ve been dosing neonitro, neophos, and tropic marin carbo calcium.
Parameters were aparently not fine for months if you've been bottoming out nutrients and messing with alkalinity, right?

Double check the pH pen's calibration and make sure you can get sane readings on a known source like your tap water (usually 7) or freshly mixed seawater (usually 8). Look up your water report, or call your water company, to find out what the tapwater's pH should be. A calibration solution can be used, if necessary, but using something you already have is nice.

Seems like your magnesium is pretty low too...not a coral issue, but makes me wonder about testing error and the salt mix you are using. Did you remix it before scooping out of it? Ca, alk and salinity seem OK. NO3 and PO4 are both still on the low side if you are having coral issues. Raise PO4 to 0.10 ppm and hold it there. As long as 5 ppm is as low as NO3 goes, that's OK, but if you see it lower than that, use a higher target for dosing. You having nothing to worry about from "overdoing it", so dosing up to 10 or 15 ppm would be fine if it seems necessary to get the minimum level you want (and not lower).
 

Randy Holmes-Farley

Reef Chemist
View Badges
Joined
Sep 5, 2014
Messages
89,598
Reaction score
93,010
Location
Massachusetts, United States
Rating - 0%
0   0   0
Seawater will not be stable at pH 9. That value is almost certainly test error, and if somehow was accurate, simple aeration will rapidly lower it.

The ro/di is never worth measuring for pH since, as noted above, a normal pH meter cannot accurately read that pH due to the very low ionic strength.
 

TOP 10 Trending Threads

HOW DO YOU ADJUST YOUR CUC AS ALGAE DISAPPEARS?

  • Capture and re-home CUC

    Votes: 10 8.4%
  • Increase white light/hours in tank to spur algae growth to feed CUC

    Votes: 8 6.7%
  • Feed nori to support CUC

    Votes: 39 32.8%
  • Feed herbivore pellets to support CUC

    Votes: 42 35.3%
  • Allow attrition to balance CUC and algae

    Votes: 51 42.9%
  • Provide macro algae to feed CUC

    Votes: 8 6.7%
  • Introduce CUC predators

    Votes: 1 0.8%
  • Other (please explain)

    Votes: 12 10.1%
Back
Top