Tropic Marin Plus NP reducing pH?

BlueTide · May 5, 2026

Has anyone heard of Plus NP significantly reducing pH? I have an established tank thats running for several years at a consistent pH of 8.4 during the day and 8.3 at night.

I just started dosing TM Plus NP 2 days ago and noticed this AM that my pH is now at 7.9!

Note, I also started dosing aminos (acro power) the same time I started Plus NP.

Searched online and havent found many cases of Plus NP or aminos reporting to lower pH when used as directed.

I understand that Plus NP contains ammonium (NH4) which in theory should lower pH, however I also understand that NH4 is a relatively weak acid. I am using both +NP and aminos as directed.

I am adding 1 pump (which equates to 1ml) per 26 gallons of +NP. System volume is 81 gallons and have been adding 3 pumps.

As far as aminos go, I am adding 15ml of acro power.

Keep in mind the tank has only received 2 doses of both.

Params as of this AM:
Alk - 8.8
Ca - 430
PO4 - 0.01
NO3 - 0
Ph: 7.9

Params as of 5/3 (taken in PM)
Alk - 8.1
Ca - 410
PO4 - 0
NO3 - 0
pH - 8.4

Skippy The Meh · May 5, 2026

In the morning PH will always be significantly lower, assuming you have your light run on a normal schedule. Try comparing numbers at same time of day.

Randy Holmes-Farley · May 5, 2026

TM Plus NP includes organic carbon so some pH lowering should be expected, though the drop you see seems pretty large to me.

BlueTide · May 5, 2026

Update - pH climbed back to 8.1

BlueTide · May 8, 2026

Update

Looks like I found the culprit.

The other day I noticed my skimmer wasn't producing many bubbles. Cleaned out a small mass of chaeto that got into the skimmer and was inhibiting bubble production.

The lack of gas exchange must have allowed CO2 to concentrate and cause a decline in pH.

2 days after fixing the issue my pH is back to 8.2 during the day and 8.1 at night (even while continuing to dose Plus NP).