Alkalinity rising?

[griff500]

I'm finally getting to the point where my GHA garden is dying off and I expect it to all be gone shortly. My previous high pH levels are dropping back down - it had been swinging between 8.2 to as much as 8.8 but is now between 8.2 and 8.4 and I think it will be back to the old range of 8 to 8.2 soon. I presume the GHA was linked to the pH levels.

Nitrate has gone from not being able to lower it to not being able to raise it above an alleged zero (Red Sea test kit), seemingly regardless of how much I feed. Phosphate seems to be stabilising at around 0.03 and going down after ages getting it out of the system.

I am now getting SPS surviving and some showing signs of growth. Yay... progress.

The odd thing is that alkalinity appears to be going up. I am still measuring on a daily basis and this apparent increase isn't due to water changes. Alkalinity is measured using Hanna.

I'm not currently dosing - just weekly 8% water changes using Tropic Marin Pro Reef - but have a calcium reactor ready to go but the increased vibrancy of my SPS and the growth doesn't appear to be lowering alkalinity - quite the opposite. Given previous issues the tank is currently only stocked with about 10 frags.

Is there any imbalance that could cause the testing to be off or to increase alkalinity? Could pH lowering do this, or high pH have given a false low reading for alkalinity or suppressed it? I test Mg and Ca from time to time and they always seems to be in the right range. I am running Zeovit and, given the low nutrient levels that I am now getting, I'm concerned about the apparent increase of alkalinity from around 7.3/7.5 to today's reading of 8.5, the rise happening during the course of this week and seeming to coincide with a significant paling and dying off of the GHA.

Thoughts?

 

[Cory]

Well id say your water changes could be contributing to an increase in alkalinty. Whats fresh saltwater read for alk?

 

[griff500]

I did say that it's not that. Increasing days after the small change and measured daily and increasing daily.

 

[Randy Holmes-Farley]

Are you using tap water for top off? Are you maintaining the water level so salinity is not increasing day to day?

The only way that alkalinity increases in a reef tank aside from additions of some sort (even if you do not know what additive or water source might contain it) is if nitrate is falling due to consumption by organisms. Reduction in nitrate of 50 ppm will increase alkalinity by 2.3 dKH.

I don't believe your pH actually reached 8.8 unless you overdosed alkalinity greatly, but daily changes in pH won't alter the alkalinity. I do not expect it impacts the Hanna measurement, but it is not a normal titration for alkalinity and I'm not certain how pH impacts its measurement. Hanna has told me it doesn't, but I cannot independently confirm that.

 

[Randy Holmes-Farley]

I should have mentioned that artificial rock made from cement can also raise alk until fully cured. Do you have cement in the tank?

 

[griff500]

Hi Randy,

Double DI for the water and an ATO being used. Salinity measured by Apex to show fluctuations and it doesn't seem to vary. Checked weekly with a refractometer.

The reported pH level could have been false (Apex) BUT it is now falling back to the range I mentioned, seemingly directly related to the GHA dying off (becoming paler and disappearing). There was a lot and I wouldn't be surprised if it was creating the big swings in pH.

Nitrate will not rise above a reported zero (Red Sea kit), having previously been at higher levels (not problem levels) and refusing to drop. It doesn't matter how much I feed. I have PLENTY of fish and so there is no shortage of waste.

I presumed you couldn't have too much filtration as bacteria would only exist at levels that could consume available food sources. I have Zoelite (not changed all that regularly) and a Marine Pure block - plenty of filtration, with bacteria fuelled by the recommended amount of Start3 (carbon dosing) for my system size. Perhaps I'm over-feeding the bacteria and I need to reduce the dose?

 

[griff500]

I should have mentioned that artificial rock made from cement can also raise alk until fully cured. Do you have cement in the tank?

Real Reef Rock (the product) was used. It was absolutely covered in GHA for quite some time due to using Triton and having an algae bed that was of insufficient size (in my opinion). I believe the rock became clogged up and saturated with phosphate but I now seem to have pulled it out based on the reaction of the GHA. It took about 6 months and is now disappearing rapidly.

 

[griff500]

As an aside, the carbon source (Start3) contains some nitrate.

 

[Randy Holmes-Farley]

Hi Randy,

Double DI for the water and an ATO being used. Salinity measured by Apex to show fluctuations and it doesn't seem to vary. Checked weekly with a refractometer.

The reported pH level could have been false (Apex) BUT it is now falling back to the range I mentioned, seemingly directly related to the GHA dying off (becoming paler and disappearing). There was a lot and I wouldn't be surprised if it was creating the big swings in pH.

Nitrate will not rise above a reported zero (Red Sea kit), having previously been at higher levels (not problem levels) and refusing to drop. It doesn't matter how much I feed. I have PLENTY of fish and so there is no shortage of waste.

I presumed you couldn't have too much filtration as bacteria would only exist at levels that could consume available food sources. I have Zoelite (not changed all that regularly) and a Marine Pure block - plenty of filtration, with bacteria fuelled by the recommended amount of Start3 (carbon dosing) for my system size. Perhaps I'm over-feeding the bacteria and I need to reduce the dose?

Bacteria do not impact alkalinity.

Dead organisms decaying may release organics that are degrading to CO2 and possibly some organic acids that are lowering pH. That wouldn't raise alkalinity.

 

[Randy Holmes-Farley]

As an aside, the carbon source (Start3) contains some nitrate.

Why do you think it contains nitrate?

 

[griff500]

Why do you think it contains nitrate?

It seems to be a fairly well-recognised 'fact' according to the Zeo threads and forum.

 

[griff500]

Bacteria do not impact alkalinity.

Dead organisms decaying may release organics that are degrading to CO2 and possibly some organic acids that are lowering pH. That wouldn't raise alkalinity.

You mentioned that nitrate being consumed by organisms could raise alkalinity - I take it you did not mean bacteria.

If it isn't too much bacteria reducing nitrate being responsible for an increased alkalinity reading then I wonder what else, if anything, it could possibly be. Perhaps the Hanna reagent is going off, although I have been testing so frequently that I doubt it would get the chance!

 

[Cory]

I wouldnt rely on hanna only for alkalinity. Ive gotten bad batches before. If you get a salifert or similar alk test, make a alk standard. 1.135g of baking soda in 1 liter pure water = 10dkh

 

[griff500]

I wouldnt rely on hanna only for alkalinity. Ive gotten bad batches before. If you get a salifert or similar alk test, make a alk standard. 1.135g of baking soda in 1 liter pure water = 10dkh

I woulnd't expect the same bottle of reagent to gradually show an increased reading each day though - it has been a fairly consistent rise from a previous consistently stable level.

 

[Randy Holmes-Farley]

It seems to be a fairly well-recognised 'fact' according to the Zeo threads and forum.

Just seems weird since it says it decreases nitrate.

 

[Randy Holmes-Farley]

You mentioned that nitrate being consumed by organisms could raise alkalinity - I take it you did not mean bacteria.

If it isn't too much bacteria reducing nitrate being responsible for an increased alkalinity reading then I wonder what else, if anything, it could possibly be. Perhaps the Hanna reagent is going off, although I have been testing so frequently that I doubt it would get the chance!

I do mean bacteria, or corals, macroalgae, etc.

But having a lot of any of them is not sufficient. Nitrate must be declining (not just low). In a steady state nitrate situation (whether high or low), the alk is depleted by the production of nitrate, and exactly added back by the consumption of nitrate. So no net effect happens to alk unless nitrate is changing.

 

[griff500]

Just seems weird since it says it decreases nitrate.

It does, but I believe the idea is to ensure that there is some nitrate available to assist with keeping phosphate levels down on the basis that you're not going to consume phosphate without some nitrate. Something like that.

 

[griff500]

I do mean bacteria, or corals, macroalgae, etc.

But having a lot of any of them is not sufficient. Nitrate must be declining (not just low). In a steady state nitrate situation (whether high or low), the alk is depleted by the production of nitrate, and exactly added back by the consumption of nitrate. So no net effect happens to alk unless nitrate is changing.

Ok... back to square one then! lol

I'm going to try another bottle of reagent but I wouldn't expect an issue with the reagent to gradually give a higher reading each day. Could the algae die-off be providing something that could influence this?

 

[Randy Holmes-Farley]

Ok... back to square one then! lol

I'm going to try another bottle of reagent but I wouldn't expect an issue with the reagent to gradually give a higher reading each day. Could the algae die-off be providing something that could influence this?

I doubt it.

 

[griff500]

Sigh... There must be a reason.