Alkalinity going up instead of down

[jurgenph]

One of my tanks has a weird Alk issue.
It keeps going up all by itself.

It's a 10 gallon aio.
No skimmer.

Test at 9.8 dKh
Two weeks later, water change.
Test at 9.4 dKh.
Two weeks later, no water change.
Test at 9.9 dKh.

I DO dose NaNO3 to keep nitrates up.

Over the last few weeks I raised nitrates to 10 ppm

Last test they were slightly below 5 ppm.

Is this a case of bacteria processing nitrates and returning Alk back into the water?

I'm really puzzled.

I'm not dosing anything.

My ATO if filled with zero TDS RODI.

My fresh salt mix water tests at 8.something dKH.


J.

 

[spidercrab]

Might just be testing error. What test are you using? many of them arent very exact and .5dkh isnt a large difference on most of them. In my opinion I would just average those 3 results and say your DKH has probably been about 9.7 all along.

 

[The Aquatic Arsenal]

I am thinking test kit as well.

 

[jurgenph]

i'm testing with hanna Alk tester.
i'm pretty sure it's not testing error.
my other tank tests as expected, and my freshly mixed up water tests as expected too.

J.

 

[Randy Holmes-Farley Verified Community Expert]

Consumption of nitrate raises alk. That’s the likely source.

 

[Tamberav]

+1 above... I had the same problem when I had to dose nitrates to keep them up.

 

[jurgenph]

Consumption of nitrate raises alk. That’s the likely source.

+1 above... I had the same problem when I had to dose nitrates to keep them up.

so basically, i need to wait until the livestock in this tank starts growing and outcompete the bacteria for nitrates?

looks like i need to start stocking more LOL


thanks folks!

J.

 

[Randy Holmes-Farley Verified Community Expert]

so basically, i need to wait until the livestock in this tank starts growing and outcompete the bacteria for nitrates?

looks like i need to start stocking more LOL


thanks folks!

J.

Any organism taking up nitrate adds alkalinity. Corals, bacteria, algae, etc.

 

[Magellan]

Any organism taking up nitrate adds alkalinity. Corals, bacteria, algae, etc.

but corals also consume alk. Surely there is a net loss of alk from keeping corals in the tank?

 

[Randy Holmes-Farley Verified Community Expert]

but corals also consume alk. Surely there is a net loss of alk from keeping corals in the tank?

Hard corals, yes. Soft corals, maybe not.

 

[Magellan]

All I know is I have to dose Alk or it drops, and I had to dose even before I started putting SPS in the tank. Would that be a thing only if you were actually dosing nitrates?

 

[Justfebreezeit]

Also since the water volume is so small maybe the slight swing in salinity from in between when the ATO finally gets tripped might play a roll

All I know is I have to dose Alk or it drops, and I had to dose even before I started putting SPS in the tank. Would that be a thing only if you were actually dosing nitrates?

Coralline is a good consumer of Alk if you have that growing, other than that maybe? Could be a few different reasons i'd imagine.

 

[Randy Holmes-Farley Verified Community Expert]

All I know is I have to dose Alk or it drops, and I had to dose even before I started putting SPS in the tank. Would that be a thing only if you were actually dosing nitrates?

no, many organisms and abiotic precipitation of calcium carbonate consume alk. Dosing nitrate adds alk, it doesn’t deplete it.

 

[CMO]

Could it be due to rising phosphate levels? I base that on the fact that running GFO reduces alk, so by similar reasoning perhaps rising phosphate levels could be the cause of rising alk?

I have a new tank starting up at the moment and my alk is also very slowly increasing without dosing any alk. My phosphate levels are rising, however, which I think may be causing this, but not sure.

 

[Magellan]

Could it be due to rising phosphate levels? I base that on the fact that running GFO reduces alk, so by similar reasoning perhaps rising phosphate levels could be the cause of rising alk?

I have a new tank starting up at the moment and my alk is also very slowly increasing without dosing any alk. My phosphate levels are rising, however, which I think may be causing this, but not sure.

Ahh that makes sense. I use a product called Phosguard in my nano to remove phosphates. Not sure if I still need this all the time, but I’ve been really hesitant to change anything as my tank is doing great!

 

[Randy Holmes-Farley Verified Community Expert]

Could it be due to rising phosphate levels? I base that on the fact that running GFO reduces alk, so by similar reasoning perhaps rising phosphate levels could be the cause of rising alk?

I have a new tank starting up at the moment and my alk is also very slowly increasing without dosing any alk. My phosphate levels are rising, however, which I think may be causing this, but not sure.

phosphate addition and consumption does not generally impact alkalinity since what it adds when you add it is taken out when it is used. But true if nitrate. You’d need huge phosphate levels for it to be a substantial part of measured alk.

 

[merereef]

Consumption of nitrate raises alk. That’s the likely source.

Never thought of that, my nitrates were on 25 started lowering and noticed alk going up

 

[CMO]

phosphate addition and consumption does not generally impact alkalinity since what it adds when you add it is taken out when it is used. But true if nitrate. You’d need huge phosphate levels for it to be a substantial part of measured alk.

I see. So then when GFO reduces alk that is not due to the reduction in phosphate? Or is it but the correlation only goes one way? Thanks

 

[Acros]

I am seeing Alk rising in my tank. I use a Hanna checker. I added chaeto at the stating of this. I have not seen a lot of growth anyway. My phosphates are at 0.07ppm, Nitrates between 0 and 0.5ppm. I do not have any corals in the tank now (I had a mass dieoff about 2 weeks back). The tank is 3 months old. I do not dose anything. I do 10% water changes every week using instant ocean reef crystals.

Edit: Is it safe to add corals in a week or two? Ph is 8.0

 

[dvgyfresh]

I am seeing Alk rising in my tank. I use a Hanna checker. I added chaeto at the stating of this. I have not seen a lot of growth anyway. My phosphates are at 0.07ppm, Nitrates between 0 and 0.5ppm. I do not have any corals in the tank now (I had a mass dieoff about 2 weeks back). The tank is 3 months old. I do not dose anything. I do 10% water changes every week using instant ocean reef crystals.

I was having this issue as well with instant ocean salt it was mixing at 1.026 salinity and dkh at 16 but I used tap water + instant ocean . ( now use only lfs saltwater as mixing salt creates too much for me , 1600 Mg , 500 Calc and 16 dkh)