Alkalinity dropping in FOWLR - Please help me understand WHY!

TexanCanuck · Mar 20, 2021

Question 1: Can someone please explain the chemistry behind why the alkalinity in my FOWLR tank keeps dropping, even with dosing liquid soda ash daily @ 40ml per day, and all while calcium and magnesium remains constant?

Question 2: Based on the answer above, what should I do differently?

NOTE - I apologize in advance for the length of this post ... since I'm not sure which data is relevant, I've chosen to err on the side of giving you everything!

Background:

Tank has only been running for 2.5 months (started cycling on Jan 1!)
My goal is a mixed reef tank (LPS + Softies mainly) but don't want to add corals yet
I have a 130g DT (140g total water volume with sump, sand, and live rock) supported by the following equipment:
- Trigger Platinum Sump with Fleece Roller
- 4x Brightwell Aquatics Xport-BIO bricks + 2x Brightwell Aquatics Xport-NO3 bricks (in sump)
- Reef Octopus - Regal 200EXT (with CO2 scrubber on air inlet)
- GAC reactor w/ ~1 cup of BRS Bulk Premium ROX 0.8 Aquarium Carbon with water flow @ ~ 50 GPH
- Refugium w/ ~ 1lb (16Oz) of Red Pom Pom (Gracilaria Hayi) illuminated with Kessil A360W Tuna Sun
- 2 x Pentair Aquatics Smart UV 25 Watt (processing at ~375 GPH ... each powered by its own return pump)
- 3 x Radion XR15 G5 PRO LED Lights
- Apex
- Triton
- DOS + DDR (for 2-part dosing)
In the display tank there is:
- 40 Lbs Live Sand
- 130 Lbs MarcoRocks Dry Rock
- 20 Lbs of aquacultured Live Rock from FLA
Livestock:
- 1 x Blonde Naso Tang (~3")
- 1 x Sailfin Tang (~3")
- 1 x Yellow Tang (~4")
- 1 x Purple Tang (~4")
- 1 x Pakistan Butterflyfish (~1.5")
- 1 x Midas Blenny (~4")
- 1 x Flame Hawkfish (~1.5")
- 1 x Blue Dot Jawfish (~3")
- 2 x Gladiator Clownfish (~1.5")
- 9 x Azure Damselfish (1.5")
- 2 x Scarlet Cleaner Shrimp
- 2 x Fire Shrimp
- 1 x Coral Banded Shrimp
- 2 x Emerald Crab
- CUC - Assorted snails, hermit crabs, conch
- NOTE: My goal is add corals once I see coralline algae taking off - but until then, this is a fish-only setup
Typical Water Parameters
- Water made from RODI + Tropic Marin PRO Reef
- Temp: 77.9 - 78.3F
- pH: 8.11 - 8.36
- Salinity: 35 ppt
- ALK: (see below)
- CA: 470 - 503ppm (via Triton)
- MG: 1290 - 1319ppm (via Triton)
- Ammonia: <0.02ppm (via Seneye Reef)
- Nitrite: <0.05ppm (via Hanna Checker) - I know this doesn't matter, but there you go ...
- Nitrate: <2ppm (via Hanna Checker) - OFTEN find ZERO - at which point I turn down the photoperiod on the refugium and/or increase feeding to fish
- Phosphate: <0.01 (via Hanna Checker) - OFTEN find ZERO - at which point I dose Brightwell Aquatics NeoPhos
- I perform a 20% water change weekly
2-Part Dosing
- NOTE: I know that 2-part dosing is NOT required with a FOWLR ... I installed the Trident and DOS + DDR only to get ready for when I add corals
- However, after seeing Alkalinity dropping steadily with only fish in the tank, I did a 1-time correction with Liquid Sodium Bicarb then started automatic dosing of Liquid Soda Ash (all from BRS using their "Pharma-grade" pouches)
- I initially started out with very small alkalinity doses twice per day, and every week would do a new "adjustment dose" then re-calculated what daily dose needed to be based on the 7-day total ... I am now up to dosing 40ml per day (with DOS automatically adjusting dose in response to readings from Triton)
- Throughout all of this both Calcium and Magnesium have remained fairly constant, so I have not been dosing any of them. I know this shouldn't make sense if I had corals or even a lot of coralline algae - I should need to dose both CA and ALK in equal measure. However, my assumption was that I'm not seeing any drop in CA or MG becasue right now the tank is fish only

HERE'S THE PROBLEM: Alkalinity and Liquid Soda Ash dosing with only fish in the tank (and a SMALL bit of coralline algae on the real live rock):

I found a number of articles on R2R by Randy Holmes-Farley that make it clear to me I'm doing SOMETHING WRONG ... but I'm not smart enough to figure out exactly what!

Again, I have two questions:

Can someone please help me understand the chemistry behind why my alkalinity keeps falling even though I keep increasing my daily dosing of Liquid Soda Ash - all while the tank is still fish-only?
Based on the answer to the question above, tell me what I should be doing differently?

My hypothesis is that either (A) I am chasing a number (alkalinity) that simply doesn't matter (as long as pH is stable, of course) while I still only have fish in the tank, or (B) if I started dosing Calcium in equal measure to Alkalinity this will magically stop [but I have a hard time understanding why that might be the case].

Thoughts?

Oregon Grown Reef · Mar 20, 2021

TexanCanuck said:
Question 1: Can someone please explain the chemistry behind why the alkalinity in my FOWLR tank keeps dropping, even with dosing liquid soda ash daily @ 40ml per day, and all while calcium and magnesium remains constant?

Question 2: Based on the answer above, what should I do differently?

NOTE - I apologize in advance for the length of this post ... since I'm not sure which data is relevant, I've chosen to err on the side of giving you everything!

Background:

Tank has only been running for 2.5 months (started cycling on Jan 1!)

My goal is a mixed reef tank (LPS + Softies mainly) but don't want to add corals yet

I have a 130g DT (140g total water volume with sump, sand, and live rock) supported by the following equipment:

Trigger Platinum Sump with Fleece Roller

4x Brightwell Aquatics Xport-BIO bricks + 2x Brightwell Aquatics Xport-NO3 bricks (in sump)

Reef Octopus - Regal 200EXT (with CO2 scrubber on air inlet)

GAC reactor w/ ~1 cup of BRS Bulk Premium ROX 0.8 Aquarium Carbon with water flow @ ~ 50 GPH

Refugium w/ ~ 1lb (16Oz) of Red Pom Pom (Gracilaria Hayi) illuminated with Kessil A360W Tuna Sun

2 x Pentair Aquatics Smart UV 25 Watt (processing at ~375 GPH ... each powered by its own return pump)

3 x Radion XR15 G5 PRO LED Lights

Apex

Triton

DOS + DDR (for 2-part dosing)

In the display tank there is:

40 Lbs Live Sand

130 Lbs MarcoRocks Dry Rock

20 Lbs of aquacultured Live Rock from FLA

Livestock:

1 x Blonde Naso Tang (~3")

1 x Sailfin Tang (~3")

1 x Yellow Tang (~4")

1 x Purple Tang (~4")

1 x Pakistan Butterflyfish (~1.5")

1 x Midas Blenny (~4")

1 x Flame Hawkfish (~1.5")

1 x Blue Dot Jawfish (~3")

2 x Gladiator Clownfish (~1.5")

9 x Azure Damselfish (1.5")

2 x Scarlet Cleaner Shrimp

2 x Fire Shrimp

1 x Coral Banded Shrimp

2 x Emerald Crab

CUC - Assorted snails, hermit crabs, conch

NOTE: My goal is add corals once I see coralline algae taking off - but until then, this is a fish-only setup

Typical Water Parameters

Water made from RODI + Tropic Marin PRO Reef

Temp: 77.9 - 78.3F

pH: 8.11 - 8.36

Salinity: 35 ppt

ALK: (see below)

CA: 470 - 503ppm (via Triton)

MG: 1290 - 1319ppm (via Triton)

Ammonia: <0.02ppm (via Seneye Reef)

Nitrite: <0.05ppm (via Hanna Checker) - I know this doesn't matter, but there you go ...

Nitrate: <2ppm (via Hanna Checker) - OFTEN find ZERO - at which point I turn down the photoperiod on the refugium and/or increase feeding to fish

Phosphate: <0.01 (via Hanna Checker) - OFTEN find ZERO - at which point I dose Brightwell Aquatics NeoPhos

I perform a 20% water change weekly

2-Part Dosing

NOTE: I know that 2-part dosing is NOT required with a FOWLR ... I installed the Trident and DOS + DDR only to get ready for when I add corals

However, after seeing Alkalinity dropping steadily with only fish in the tank, I did a 1-time correction with Liquid Sodium Bicarb then started automatic dosing of Liquid Soda Ash (all from BRS using their "Pharma-grade" pouches)

I initially started out with very small alkalinity doses twice per day, and every week would do a new "adjustment dose" then re-calculated what daily dose needed to be based on the 7-day total ... I am now up to dosing 40ml per day (with DOS automatically adjusting dose in response to readings from Triton)

Throughout all of this both Calcium and Magnesium have remained fairly constant, so I have not been dosing any of them. I know this shouldn't make sense if I had corals or even a lot of coralline algae - I should need to dose both CA and ALK in equal measure. However, my assumption was that I'm not seeing any drop in CA or MG becasue right now the tank is fish only

HERE'S THE PROBLEM: Alkalinity and Liquid Soda Ash dosing with only fish in the tank (and a SMALL bit of coralline algae on the real live rock):

I found a number of articles on R2R by Randy Holmes-Farley that make it clear to me I'm doing SOMETHING WRONG ... but I'm not smart enough to figure out exactly what!

Again, I have two questions:

Can someone please help me understand the chemistry behind why my alkalinity keeps falling even though I keep increasing my daily dosing of Liquid Soda Ash - all while the tank is still fish-only?

Based on the answer to the question above, tell me what I should be doing differently?

My hypothesis is that either (A) I am chasing a number (alkalinity) that simply doesn't matter (as long as pH is stable, of course) while I still only have fish in the tank, or (B) if I started dosing Calcium in equal measure to Alkalinity this will magically stop [but I have a hard time understanding why that might be the case].

Thoughts?

Two things I can think of.

Is it precipitating out somwhere? Notice any white crust on the pumps or wavemakers?

The other thing I can think of is your nitrates are raising...but you said they're low. If they're low, why are you doing water changes? As nitrates rise, alkalinity drops. Here's a quote from @Randy Holmes-Farley:

"The conversion of ammonia to nitrate depletes alkalinity, so if nitrate is rising, then alkalinity can be depleted by this process."

Thing is, once your nitrates are used up by the algae in your refugium, the alkalinity raises again. If you do a water change, the alkalinity is lost.

I have no clue otherwise what it could be.

TexanCanuck · Mar 20, 2021

Hmm ... that's very interesting ... I did not know there was a relationship between alkalinity and nitrates!

With respect to abiotic precipitation, I believe the answer is NO - I have not had any problems with calcification of my pump impellers, heaters, or anything else (that I know of, but now I'm going to check!)

Thank you for the hint about nitrate levels. I'm going to try taking readings more frequently and see how much they fluctuate and if they fluctuate in sync with alkalinity. Right now my nitrates are typically very low, as my macroalgae has proven very effective at nutrient export.

As for water changes, I keep them up because (A) it has been a deeply-ingrained habit, (B) they are really easy to do, and (C) everything I have ever read has led me to believe that even with low nitrates and phosphates, water changes are still a good thing to deal with all the other pollutants that may be in your water that you're not testing for.

Need to do some more research...

Courtney Aldrich · Mar 21, 2021

TexasCanuck (that's a beautiful blue-spotted jawfish!) metabolism of organic compounds (food) can produce acid (organic acids) under low oxygen and anaerobic conditions while oxidation of ammonia to nitrate produces lots of protons that also tend to consume alkalinity (HCO3- + H+ = H2CO3 = CO2 + H20, i.e. you are losing your alkalinity through CO2 degassing). In an established reef tank where efficient denitrification occurs (conversion of nitrate to N2), protons are consumed, which balances out the protons produced during ammonia oxidation. Similarly, an established reef tank also has a lot of bacteria that can oxidize byproduct organic acids all the way to CO2. In a new system, I don't believe you have yet established denitrifies or bacteria capable of oxidizing all organic acids, so you can see a drop in alkalinity without consumption of calcium or magnesium. I am having the same issues with my tank, which was set up only 2 days after you.

TexanCanuck · Mar 21, 2021

Thank you for helping me understand the chemistry!

If I am following you then, the next steps for me would be to continue liquid soda ash dosing and simply increasing the dosage until the tank stabilizes at a given total alkalinity?

Am I correct in NOT also dosing calcium?

BTW - that's my buddy Bob ... my blue-spotted jawfish and my favorite in the whole tank (but don't tell the others)

TexanCanuck · Mar 21, 2021

Follow on question ...

If this is perfectly normal for a tank to consume alkalinity until it builds up a strong enough colony of facultative bacteria, why do so many people tell you not to worry about dosing if you're going to build a FOWLR system? WOuldn't they have the same problem? Shouldn't EVERY new tank have to be concerned about dosing alkalinity for a considerable period of time?

Courtney Aldrich · Mar 21, 2021

TexanCanuck said:
Thank you for helping me understand the chemistry!

If I am following you then, the next steps for me would be to continue liquid soda ash dosing and simply increasing the dosage until the tank stabilizes at a given total alkalinity?

Am I correct in NOT also dosing calcium?

BTW - that's my buddy Bob ... my blue-spotted jawfish and my favorite in the whole tank (but don't tell the others)

I have been 'reefing' for about 2 months so I will leave it up to the experts here, but I would not dose calcium since you are not consuming any. The problem of dosing just sodium bicarbonate is that you will accumulate sodium over time and you're dosing a goodly amount. The two part tries to balance this out by dosing calcium chloride where the chloride pairs with the sodium to keep your ions balanced. However, you are doing monster 20% weekly water changes, so you will not accumulate anything and can keep dosing sodium bicarbonate to your heart's content.

When dosing things daily, you can really accumulate things if you don't pay attention and do nominal water changes. I estimate you are dosing about 2 ppm of sodium per day, which translates to about 60 ppm in a month, which is not a lot, but if you do 20% monthly water changes (typical of many people, I know you are doing this weekly), you would ultimately reach a steady-state level of 330 ppm additional sodium (I calculate for a 20% monthly change that you reach 5.5X the monthly dosing level). Considering seawater is 10,500 ppm this is not a big deal, but it can rapidly get out of control if you're not careful. For instance, I am dosing 8 ppm sodium daily to maintain my alkalinity (using sodium carbonate, 'baked' baking soda), which gives me 240 ppm every month. With only a 20% monthly water change, I will accumulate 1320 ppm sodium over time, which is a problem!

terraincognita · Mar 21, 2021

TexanCanuck said:
Thank you for helping me understand the chemistry!

If I am following you then, the next steps for me would be to continue liquid soda ash dosing and simply increasing the dosage until the tank stabilizes at a given total alkalinity?

Am I correct in NOT also dosing calcium?

BTW - that's my buddy Bob ... my blue-spotted jawfish and my favorite in the whole tank (but don't tell the others)

Have you been verifying your Alk levels with a manual test as well or just the APEX?

Tanks naturally will also have Alk swings with PH swings over day and night. As you can see if your graph the Alk is returning back to the higher ranges. Unless that's only after you dosing? Don't look at it at an hourly basis rather the peaks daily is probably better.

The more i think about this too definitely needs a chemist opinion.

I know that Soda Ash REACTS in the water thereby giving you an increase in PH and Alk, Wondering if possibly you're dosing into nothing since the ash doesn't have any extra free hydrogen to take away due to other things going on in an establishing tank.

Oof this is too much chemistry for my brain this late.

TexanCanuck · Mar 21, 2021

terraincognita said:
Have you been verifying your Alk levels with a manual test as well or just the APEX?

Yes - I confirm the reading reported by the Trident once a week using a Hanna Checker

Randy Holmes-Farley · Mar 22, 2021

The conversion of ammonia to nitrate is not what is causing an apparent drop in alkalinity in this case because (if you believe the nitrate test kit), nitrate is not accumulating. If nitrate is not accumulating, there is no drop in alk from its production because its consumption adds back the alkalinity.

I expect it is formation of calcium carbonate, either by abiotic precipitation of calcium carbonate, or by coralline algae, or both. A soft coral only tank can use 2 dKH per day.

You are only using 0.4-0.5 dKH per day, I doubt you can accurately detect the matching calcium drop of 3 ppm per day and you certainly will not detect the expected drop in magnesium of much less than 1 ppm per day. Water changes may keep these small drops propped up.

Just keep dosing the alkalinity as needed to maintain 7 dKH.

TexanCanuck · Mar 22, 2021

Thank you Randy and everyone!

This gives me much more peace of mind

Bradley Creek Reefer · May 26, 2021

Randy Holmes-Farley said:
The conversion of ammonia to nitrate is not what is causing an apparent drop in alkalinity in this case because (if you believe the nitrate test kit), nitrate is not accumulating. If nitrate is not accumulating, there is no drop in alk from its production because its consumption adds back the alkalinity.

I expect it is formation of calcium carbonate, either by abiotic precipitation of calcium carbonate, or by coralline algae, or both. A soft coral only tank can use 2 dKH per day.

You are only using 0.4-0.5 dKH per day, I doubt you can accurately detect the matching calcium drop of 3 ppm per day and you certainly will not detect the expected drop in magnesium of much less than 1 ppm per day. Water changes may keep these small drops propped up.

Just keep dosing the alkalinity as needed to maintain 7 dKH.

I’m having a similar issue. I am struggling to maintain my alkalinity. I’m having to dose 100ml of Red Sea alkalinity every day to maintain a stably level around 8.5. I’m dosing about 40ml of calcium a day to keep it at 450.
I have a Red Sea Reefer 250, 14 months old. Problem started about a month ago when I accidentally turned my calcium doser ON, on the Apex and it dumped 600ml of calcium into my system. Took me a couple weeks to get my levels right again but now my dosing amounts are crazy.
I’ve got a lot of LPS and they are all fine and growing. My power heads are starting to freeze up, bout to clean them. Had to clean my return pump out too bc it seized up.
What should I do now to get the dosing scheduled back to a normal Milliliter amount per day?

Screwgunner · May 26, 2021

I am at the 3 month mark and seeing the same thing. But I run a algae turf scrubber. I have 2 colonies of zoas 10 frags and two monti.

Bradley Creek Reefer · May 27, 2021

How do you correct this? When I try to back of the dosing my Alk and cal levels drop pretty fast. So I’m continuing to dump about 100 mil of Alk and 40-50mil of Cal to keep them at a stable reading. I know I’m clogging up my equipment, this has to stop. If a chemist could make a comment on this, that would be awesome.

Randy Holmes-Farley · May 27, 2021

Robs Reef 250 said:
What should I do now to get the dosing scheduled back to a normal Milliliter amount per day?

What is that alk addition in dKH per day?

Why do you think it is not "normal"?

Bradley Creek Reefer · May 27, 2021

Randy Holmes-Farley said:
What is that alk addition in dKH per day?

Why do you think it is not "normal"?

I think its not normal only because I've heard you should be dosing the same amount of Calcium and Alkalinity and that I shouldn't have to dose as much as i am for a tank that is 65 total gallons and because of the issue I had that may have started all this.

So bare with me here, my Alk is currently at 8.45 and to maintain that I am dosing 100mil of ESV B-Ionic Part A. My Calcium is 430 and I'm dosing 40 mil of B-Ionic Part B to maintain that each day. When I have tried to back off the amount I'm dosing, those parameter levels drop very fast.

This might be the kicker, about a month ago I accidentally turned my calcium doser to ON without knowing and ended up dumping 600 mil of calcium into my tank. Calcium levels went to 850. Then it threw off my alkalinity, I couldn't keep it up and it bottomed out around 4.8. I started doing water changes and dosing a lot more than my normal 40mil ALK per day to get the ALK back up. It was taking over 100 mil per day to get it up to 8.5.

Something is going on to make it where I have to dose 100 mil ALK per day to maintain 8.5 when I used to only dose 40mil per day.

I've been told it is a Precipitation issue. My question is, how do it correct the precipitation issue if that is was my issue is?

Thanks,

Robert

taricha · May 27, 2021

If you massively overdosed calcium, that could have started a precipitation event as you described. There may be precipitation still ongoing as you suspect.
Setting aside the apparent imbalance, if it were me, I'd measure Mg, bring it up to correct levels and let Ca and alk stabilize first before worrying about dosing amounts and balance.

Bradley Creek Reefer · May 28, 2021

Mag is 1350 on the Tridant.

ru4serious · May 28, 2021

Coraline algae will affect alk, is you rock turning purple

Bradley Creek Reefer · May 28, 2021

I’ve had coralline algae for a long time now. Long before I had to start dosing more. It all started with my calcium overdose. Just trying to figure out how to stop a precipitation event. Pretty sure that’s what’s going on.