STN/RTN Chemistry confusion

Caleb Hoeft · May 25, 2018

Hello there, new to the forum but not to reefing in general but need some help. I have been experiencing a lot of STN and RTN on my SPS frags. I've double check all my parameters and they're as follows:

60g cube w/ sump and open top.
Alk 9.1 (Hanna Checker)
Cal 420-440 (Red Sea Pro)
Mag 1400 (Salifert)
N03 .25 (Red Sea Pro)
P04 .04 (Red Sea Pro)
Salinity 1.025 (Refractometer)
Temp 77 degrees
I don't run any GFO but DO run carbon.
Rain 2 Algae scrubber was installed within the last month to hopefully help with the following PH issue.
Dosed Acropower weekly.

PH 7.5-7.65 * I suspect this may be the issue. But I am having a heck of a time raising it. I've had the house windows open for 2 days straight with hardly a climb. I've been running Kalk in the ATO as well as more surface agitation to increase evap and still no significant change to PH. I've orderd some CO2 reactor media to give it a whirl, but I'm hoping to avoid this beinga constant thing to use as it seems costly.*

I can say I was feeding the tank pretty sparsely, once every 3 days maybe. As a result I've kept algae growth to a minimum but I've also been wondering if nutrients are an issue more on the low end then the sweet spot in the middle. Mainly do to work scheduling was the cause of lower feeding. I have since been running an auto feeder so I'm sure nutrient levels will change but the the algae scrubber should hopefully do its job.

Randy Holmes-Farley · May 25, 2018

How are you measuring that pH? I agree it is quite low, but if it did not rise with outside air enterign the room, it may not be accurate.

in addition to recalibrating, you can try this aeration test to really see if aeration is the issue:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

Caleb Hoeft · May 25, 2018

Randy Holmes-Farley said:
How are you measuring that pH? I agree it is quite low, but if it did not rise with outside air enterign the room, it may not be accurate.

in addition to recalibrating, you can try this aeration test to really see if aeration is the issue:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

I am measuring using my tanks reefkeeper. Also, I did make sure to recalibrate it, twice in fact just in case for some weird reason my calibration packets were bad. I will do the aeration you suggested and see. I'm wondering how I will be able to do this outdoors as it is in the 90's + for temperature here and the inside temp is a 20 degree difference.

Caleb Hoeft · May 25, 2018

I forgot to mention my current Kalk dosage is @ 1tsp per gal. I could try upping it to 2tsp, but that still seems like it might be a bandaid fix.

Randy Holmes-Farley · May 25, 2018

I'd personally suspect the measurement. Quite a few folks have pH measurement issues with reef controllers, either due to electrical interference or some other issue. pH 7.5 implies a very high excess of CO2 in the water.

Assuming the pH is not really that low, I don't see a chemical issue for the problems, but being a little less aggressive on the nutrient export to raise nitrate a bit might be desirable. Maybe less hours per day lighting the algae.

Caleb Hoeft · May 25, 2018

Randy Holmes-Farley said:
I'd personally suspect the measurement. Quite a few folks have pH measurement issues with reef controllers, either due to electrical interference or some other issue. pH 7.5 implies a very high excess of CO2 in the water.

Assuming the pH is not really that low, I don't see a chemical issue for the problems, but being a little less aggressive on the nutrient export to raise nitrate a bit might be desirable. Maybe less hours per day lighting the algae.

What are your thoughts on shutting the skimmer off for a few hours a day maybe as instead or as well?

Randy Holmes-Farley · May 25, 2018

Caleb Hoeft said:
What are your thoughts on shutting the skimmer off for a few hours a day maybe as instead or as well?

i'm usually not a fan of that relative to other methods since it impacts many other things, especially aeration. In your case, I guess it also depends on if the pH is really that low.

Caleb Hoeft · May 25, 2018

Randy Holmes-Farley said:
i'm usually not a fan of that relative to other methods since it impacts many other things, especially aeration. In your case, I guess it also depends on if the pH is really that low.

Ok, I'll take a look again as well and see if there might be an electrical interference somehow with the PH probe. If the temperature drops outside enough I'll give the aeration test a shot and update as well. If the PH reading does prove to be wrong, what are you initial thoughts as to why the RTN/STN issues then? Cause I'm completely lost atm.

Randy Holmes-Farley · May 25, 2018

Caleb Hoeft said:
If the PH reading does prove to be wrong, what are you initial thoughts as to why the RTN/STN issues then? Cause I'm completely lost atm.

I'd have to say I don't see a reason for it in the data.

Caleb Hoeft · May 25, 2018

Randy Holmes-Farley said:
I'd have to say I don't see a reason for it in the data.

I haven't done so yet, but I was thinking of running the intake of my skimmer air to the garage. I don't do any work in there typically. I'm not sure if the effect of it would have any significant impact tho.

Randy Holmes-Farley · May 26, 2018

Caleb Hoeft said:
I haven't done so yet, but I was thinking of running the intake of my skimmer air to the garage. I don't do any work in there typically. I'm not sure if the effect of it would have any significant impact tho.

Garage air probably has lower CO2, but if it smells at all of chemicals like pesticides, fertilizers, etc, that might be undesirable.

Flippers4pups · May 26, 2018

As for what is causing RTN/STN, here's what I posted on another members question about this topic:

Here's a good read on the subject I found some years ago:

http://www.artificialreefs.org/Corals/diseasesfiles/Common Identified Coral Diseases.htm

My experience with RTN/STN is that fragging the coral at the infection line/sight, removing the infected tissue out of the system. Try to keep the infected tissue from becoming loose and ending up in the water collum.
(Reports of infected corals infecting other healthy corals near by)

Dip the healthy frag in a iodine bath and then into a bath of bacterial meds. Rinse and back in the tank. This doesn't always work, because of the different strains of bacteria.

RTN/STN is triggered by environmental stressors: temp, water pramameter swings, toxins.....etc....
They weaken the corals immune system, from there it's strictly speculation, but in infected tissue, bad bacteria have been found. Its not clear if the bad bacteria ( vibrio strain in most cases) was to blame or something else and the bad bacteria was there to "clean up" the dieing tissue.

Coral disease research has found 1000's of different strains of bacteria (gram positive and gram negative) living on coral colonies. These strains differ from one part of a reef to another near by. It's almost impossible to isolate these strains, thus it's difficult to know exactly how to treat them.

Unfortunately there will never be a treatment or cure, most likely in the foreseeable future.

Hope this helps.