Nitrate bottomed out from algae turf scrubber?

Kilman805 · Jul 14, 2025

I added a Santa Monica algae turf scrubber (model HOG1x) in late April to my 32 gallon tank to combat high nitrate and phosphate. At the time, nitrate was ~35 ppm and phosphate around 2 ppm. I was using Salifert tests then. Together with some water changes, nitrate seemed to be holding more or less steady and phosphate dropped to ~1 ppm. In late May I bought Hanna checkers and my levels were 25 ppm nitrate and 0.9 ppm phosphate.

All this time, the ATS growth was more purple and slimy than green. I guessed that might have to do with the phosphate being so high compared to the nitrate. So I started dosing lanthanum chloride to bring the phosphate down. That worked well and brought the phosphate down steadily at a rate that matched well to the theoretical prediction.

But now that the phosphate is lower the nitrate seems to be getting consumed much more rapidly. The ATS growth is still more purple and slimy than green and stringy.

I run the ATS 18 hours a day currently (On from 6 pm to noon, Off between noon and 6 pm).

Over the last few weeks:

6/20/25: Nitrate 17.9, Phosphate 0.59 (added LaCl2)
6/23/25: Nitrate 14.5, Phosphate 0.37 (added LaCl2)
7/1/25: Nitrate 9.1, Phosphate 0.26 (did not add LaCl2)
Today: Nitrate 0.0, Phosphate 0.21 (I checked nitrate twice)

I probably should have acted on 7/1 and not waited two weeks to test again, but here I am.

I am adding my first corals tomorrow. I just got the tracking that they are arriving. So I'm a little panicked. I know it's not good to bottom out nitrate.

I added enough Dr. Tim's ammonium chloride to add ~ 0.2 ppm ammonia. (Based on Randy's DIY nitrate dosing thread as a safe dose)

I'm guessing I should substantially back off on the time I keep the ATS lighted or maybe even leave it off until I reach a reasonable nitrate level (5-10 ppm?)

I can check again tonight and again early morning and see if I have detectable nitrate and add more ammonium chloride as needed. I have a tank full of TBS live rock running since last year, so there's no question it will convert to nitrate, but I'm not sure how fast.

Advice please?

@SantaMonica

ShakeyGizzard · Jul 14, 2025

Had a fuge do it to me also, chato was doing great with algae growing on the dividers of the fuge. bottomed out my nutrients and I had a dino fight and then a cyano fight when nutrients went to high. Sticking to a regular maint routine and regular testing has leveled things out for me.

jonelder68 · Jul 14, 2025

Dose ammonia bicarbonate or more predictable is sodium nitrate. A full 10ppm dose. Both available off Amazon. Seems we’re both struggling to find our balance points. I’d get nitrates up ASAP before you’re fighting Dino’s like I currently am.

The Complete Guide to Raising Nutrients

Raising nutrients can feel like an uphill battle for many tanks. It’s not always clear which products to use, what to dose, or which filtration methods to adjust or remove. Chronically low nutrients can influence coral bleaching, pale colors...

www.reef2reef.com

If you haven’t read this article by @Miami Reef definitely do!

Garf · Jul 14, 2025

Kilman805 said:
I added a Santa Monica algae turf scrubber (model HOG1x) in late April to my 32 gallon tank to combat high nitrate and phosphate. At the time, nitrate was ~35 ppm and phosphate around 2 ppm. I was using Salifert tests then. Together with some water changes, nitrate seemed to be holding more or less steady and phosphate dropped to ~1 ppm. In late May I bought Hanna checkers and my levels were 25 ppm nitrate and 0.9 ppm phosphate.

All this time, the ATS growth was more purple and slimy than green. I guessed that might have to do with the phosphate being so high compared to the nitrate. So I started dosing lanthanum chloride to bring the phosphate down. That worked well and brought the phosphate down steadily at a rate that matched well to the theoretical prediction.

But now that the phosphate is lower the nitrate seems to be getting consumed much more rapidly. The ATS growth is still more purple and slimy than green and stringy.

I run the ATS 18 hours a day currently (On from 6 pm to noon, Off between noon and 6 pm).

Over the last few weeks:

6/20/25: Nitrate 17.9, Phosphate 0.59 (added LaCl2)
6/23/25: Nitrate 14.5, Phosphate 0.37 (added LaCl2)
7/1/25: Nitrate 9.1, Phosphate 0.26 (did not add LaCl2)
Today: Nitrate 0.0, Phosphate 0.21 (I checked nitrate twice)

I probably should have acted on 7/1 and not waited two weeks to test again, but here I am.

I am adding my first corals tomorrow. I just got the tracking that they are arriving. So I'm a little panicked. I know it's not good to bottom out nitrate.

I added enough Dr. Tim's ammonium chloride to add ~ 0.2 ppm ammonia. (Based on Randy's DIY nitrate dosing thread as a safe dose)

I'm guessing I should substantially back off on the time I keep the ATS lighted or maybe even leave it off until I reach a reasonable nitrate level (5-10 ppm?)

I can check again tonight and again early morning and see if I have detectable nitrate and add more ammonium chloride as needed. I have a tank full of TBS live rock running since last year, so there's no question it will convert to nitrate, but I'm not sure how fast.

Advice please?

@SantaMonica

I assume you are feeding some fish or other stuff? It takes a lot of algal growth to consume nitrate in such a fashion, and by the sound of it that isn't happening in the bubbly scrubber?

bobnicaragua · Jul 14, 2025

I have bottomed out my nitrates with my refugium in the past. Growing algae only controls your nitrates. I use GFO for phosphates.

Lower the intensity and/or duration of your turf scrubber lighting. It’s working too well.

Garf · Jul 14, 2025

Kilman805 said:
The ATS growth is still more purple and slimy than green and stringy.

bobnicaragua said:
Lower the intensity and/or duration of your turf scrubber lighting. It’s working too well.

Really?

bobnicaragua · Jul 14, 2025

Garf said:
Really?

Oh sorry, I missed the part where the op said they would back off the time.

Kilman805 · Jul 14, 2025

jonelder68 said:
Dose ammonia bicarbonate or more predictable is sodium nitrate. A full 10ppm dose. Both available off Amazon. Seems we’re both struggling to find our balance points. I’d get nitrates up ASAP before you’re fighting Dino’s like I currently am.

The Complete Guide to Raising Nutrients

Raising nutrients can feel like an uphill battle for many tanks. It’s not always clear which products to use, what to dose, or which filtration methods to adjust or remove. Chronically low nutrients can influence coral bleaching, pale colors...

www.reef2reef.com

If you haven’t read this article by @Miami Reef definitely do!

Thanks. I had the Dr Tim's on hand so that's what I used. But I understand it may not be the best choice if I need to keep dosing regularly.

Kilman805 · Jul 14, 2025

Garf said:
Really?

Yes, the tank is pretty heavily stocked with fish and fed well

The ATS is definitely growing lots of "stuff" but it is more dark purple and slimy, not the green stringy algae you see. Opinions on the effectiveness of slime vs. algae seem to vary, but I found an old post where the guy from Santa Monica was saying that slime is very effective too.

There's no real explanation for where else the nitrate could be going that I can imagine.

jonelder68 · Jul 14, 2025

Kilman805 said:
Thanks. I had the Dr Tim's on hand so that's what I used. But I understand it may not be the best choice if I need to keep dosing regularly.

It’s super cheap on Amazon. Buy a bag and your set for a while. Always good to have on hand for situations like this.

Ammonia bicarbonate is awesome. But as Randy suggests it’s more easily consumed. Which I’ve found very true! So dosing it is challenging to maintain levels. I was dosing a ton to establish NO3 but never would get a reading. So dosed sodium nitrate @ 10ppm worth while still dosing the normal amount of ammonia bicarbonate. It’s to the point I’m fine tuning the ammonia to keep it maintained.

Kilman805 · Jul 14, 2025

The sodium nitrate link you sent doesn't work. Amazon links always seem to get messed up here.

From what I'm seeing, the sodium nitrate options are pretty limited. There is a lot of "curing salt" for meat preservation, but that's not pure sodium nitrate.

Can you please list more info about the one you have used?

jonelder68 · Jul 14, 2025

Kilman805 said:
The sodium nitrate link you sent doesn't work. Amazon links always seem to get messed up here.

From what I'm seeing, the sodium nitrate options are pretty limited. There is a lot of "curing salt" for meat preservation, but that's not pure sodium nitrate.

Can you please list more info about the one you have used?

Sorry didn’t post a link just saying from Amazon. But here’s what I got…

Amazon product

If that doesn’t work here’s a picture

Anything food grade will do

jonelder68 · Jul 14, 2025

For ammonia bicarbonate and PO4 just incase…

Miami Reef · Jul 14, 2025

Kilman805 said:
The sodium nitrate link you sent doesn't work. Amazon links always seem to get messed up here.

From what I'm seeing, the sodium nitrate options are pretty limited. There is a lot of "curing salt" for meat preservation, but that's not pure sodium nitrate.

Can you please list more info about the one you have used?

That's a good sign - it usually means it's food-grade. The ingredients should usually only list sodium nitrate.

In general: Food-grade = best purity.

Idech · Jul 14, 2025

Just turn off your turf scrubber for a few days and nitrates will naturally rise. Then adjust your settings.

Kilman805 · Jul 14, 2025

Miami Reef said:
That's a good sign - it usually means it's food-grade. The ingredients should usually only list sodium nitrate.

In general: Food-grade = best purity.

Not in this case. Pink curing salt for meat preservation is typically 6.25% sodium nitrate and 93.75% sodium chloride. It also contains pink dye to help avoid confusion with regular table salt.

Kilman805 · Jul 14, 2025

The stuff @jonelder68 posted is pure sodium nitrate though.

Miami Reef · Jul 14, 2025

Kilman805 said:
Not in this case. Pink curing salt for meat preservation is typically 6.25% sodium nitrate and 93.75% sodium chloride. It also contains pink dye to help avoid confusion with regular table salt.

Correct. That’s why I made sure to state that it should only contain sodium nitrate. They sell them without the extra additives or dyes.