Help me understand something about nitrates and phosphates

[Randy Holmes-Farley Verified Community Expert]

Ideally what you want is low ambient levels with high availability. More feeding, and more fish will both increase availability. This is what the ocean is like - levels are low, but there's constantly new water - so they can't be depleted.

What does it mean to you to have low ambient levels but high availability?

If phosphate is at, say, 0.01 ppm, how can one alter the availability?

 

[92Miata]

What does it mean to you to have low ambient levels but high availability?

If phosphate is at, say, 0.01 ppm, how can one alter the availability?

Forgive me - I'm being unclear with terms here.

What I mean when I use the term ambient, or latent phosphate is essentially what is floating around in the water column at your average moment - IE your testable phosphate results.


When I'm talking about phosphate availability - I'm talking about total phosphate input to the tank - IE, how much do you feed? How much goes into the tank via fish food, cycles through bacteria, plankton, fish, etc, and moves through the food webs of the tank.

In my experience - Ambient/Testable phosphate is not particularly important - it informs you on trends within the tank - and whether or not your current output and input are balanced - but it doesn't tell you the whole story.

For example - you can run high input/high output tanks that have tons of food input and tons of skimming/etc - and test zero (or within error range of zero on a hanna ULR) - and the corals do great and show no signs of phosphate deficiencies. And you can have tanks that regularly test higher than Natural Sea Water levels - and have corals that show signs of deficiencies.

What's important - IMO - is that you're adding enough food to the tank that corals are getting what they need - and that you have enough flow and export that corals aren't constantly being exposed to their own waste products. Nitrate/Phosphate tests are really a proxy measurement for the results of the [Food In - Food out] equation - when what we should really be interested in is the whole equation.

 

[Randy Holmes-Farley Verified Community Expert]

Forgive me - I'm being unclear with terms here.

What I mean when I use the term ambient, or latent phosphate is essentially what is floating around in the water column at your average moment - IE your testable phosphate results.


When I'm talking about phosphate availability - I'm talking about total phosphate input to the tank - IE, how much do you feed? How much goes into the tank via fish food, cycles through bacteria, plankton, fish, etc, and moves through the food webs of the tank.

In my experience - Ambient/Testable phosphate is not particularly important - it informs you on trends within the tank - and whether or not your current output and input are balanced - but it doesn't tell you the whole story.

For example - you can run high input/high output tanks that have tons of food input and tons of skimming/etc - and test zero (or within error range of zero on a hanna ULR) - and the corals do great and show no signs of phosphate deficiencies. And you can have tanks that regularly test higher than Natural Sea Water levels - and have corals that show signs of deficiencies.

What's important - IMO - is that you're adding enough food to the tank that corals are getting what they need - and that you have enough flow and export that corals aren't constantly being exposed to their own waste products. Nitrate/Phosphate tests are really a proxy measurement for the results of the [Food In - Food out] equation - when what we should really be interested in is the whole equation.

I agree that a measurement does not say anything individually about total input and export, but it does tell you all there is to know about bioavailability of phosphate to organisms at that time.

If the number changed later in the day, then bioavailability will change, but to an individual coral, if the water concentration is steady at, say, 0.04 ppm, it makes no difference if the situation is the result of no input and export each day, or 10 ppm of total input and export each day.

 

[92Miata]

I agree that a measurement does not say anything individually about total input and export, but it does tell you all there is to know about bioavailability of phosphate to organisms at that time.

If the number changed later in the day, then bioavailability will change, but to an individual coral, if the water concentration is steady at, say, 0.04 ppm, it makes no difference if the situation is the result of no input and export each day, or 10 ppm of total input and export each day.

Of course. I'm not arguing otherwise.

In my experience - corals don't seem to care much about phosphate concentration on the low end - what they seem to care about is whether or not they're getting a high enough quantity of phosphate to handle their daily needs - whether it be by inorganic ambient phosphate, or via particulate food sources (which are lacking in many, if not most reef tanks).

In some tanks - typically those that don't get fed a lot - you need to keep ambient levels relatively high (or dose them there) to get corals what they need.

In high input/output tanks (or high availability, low ambient) - the goal is a bit different - significantly higher fish loads, and more frequent and larger feeding both puts more consumable particulate and bacteria in the water column, and creates large spikes over the course of the day of both inorganic phosphate and food particulate. These spikes are transient - both because of consumption, and aragonite buffering - but can put significant quantities of phosphate in the water column.

These tanks don't seem to need to maintain measurable phosphates to get corals what they need. Either the corals are getting enough via particulate to offset the lower inorganic ambient levels - or they're able to acquire enough inorganic phosphate during the course of these spikes.


The OP has a 40 breeder with probably 60 gallons total - a skimmer rated to 150g, a lot of flow, a chaeto fuge he can't get to grow, has dosed vodka and vibrant off and on, and has 4 small fish - one of which is a clown goby. He started with aquacultured rock - and the tank has been up 9 months - with unmeasurable nitrates and phosphates - but he can't get corraline to grow anywhere there's light - and has had every weird low nutrient algae known to man. And he's running 9dkh, which isn't helping.

And yet, people are telling him on the first page to stop feeding because he has touches of algae. Everything about this tank screams that it needs more food.


@reef_ninja - if you're going to run your tank like this - you need more fish, and you need to feed more. And you may need to dose phosphates or nitrates in the interim.

How much are you actually feeding? How many cubes a day?

 

[reef_ninja]

@92Miata im feeding about 1.5 cubes and about 2 tsps of pellets per day. I’m also feeding 1/2 tsp reef roids 2-3 times a week. For four fish, it’s definitely heavy, which is why, in my personal experience, I’m not convinced feeding alone is enough to fix the problem. I’ll definitely continue to feed heavy, but I’ll be adding more fish as well.

Great discussion here, not sure about everyone else but I’m taking away a lot from this

 

[reef_ninja]

Alright, so with dosing sodium nitrate and sodium phosphate, I got my nitrates up. However, Im still struggling with phosphates.

I made a solution of 1/4 tsp for 500 ml of RO/DI water. Per the Calculator listed here , 1 ml of solution should raise my phosphates to .01.........

I've been dosing 6 mls of this solution every night for about a week, and my phosphates have still been zero. I noticed the day before yesterday, my SPS is really starting to take a downturn, so I dosed 20 mls yesterday (6 in the AM, 8 in the afternoon, and another 6 in the PM)...... still zero.

I dosed 6 more this morning, and another 6 this afternoon.......you can guess what the reading is.

Whats the deal? I feel like there is a sense of urgency here with SPS turning south, should I keep loading it up like this until I get a reading? What concerns are there for raising PO4 too fast?

 

[Randy Holmes-Farley Verified Community Expert]

Whats the deal? I feel like there is a sense of urgency here with SPS turning south, should I keep loading it up like this until I get a reading? What concerns are there for raising PO4 too fast?

The deal is dose more. maybe way more. It takes way more than a calculated amount.

Most of what you are adding is likely binding to exposed calcium carbonate surfaces.

 

[reef_ninja]

The deal is dose more. maybe way more. It takes way more than a calculated amount.

Most of what you are adding is likely binding to exposed calcium carbonate surfaces.

That makes me feel better. I think because the nitrates came up so fast, I was expecting the same for the phsophates. Ill keep going till I get a reading.

What's nice is we are still on break, so I can dose three times a day and re-check. Thanks again Randy, truly.

 

[reef_ninja]

OK, probably a rash move, but again I think there’s some urgency here. I’ve generally been fairly patient, but we’re going on a year here and not seeing even half the results I’ve had in the past, so my patience is starting to wear.

So I dumped 3 fluid ounces of my sodium phosphate solution into the tank. I now have readable phosphates. A little high at 1ppm, but I’ll retest tonight and tomorrow morning. Duncan’s don’t seem all that excited about having that much po4 dumped in at once, but everything else seems visually unaffected.

 

[blasterman]

I've been dosing my 20L which has large amounts of fast growing SPS with Seachem Phosphorus. The Seachem product is .5 % phosphorus, and I dose two cap fulls a week to keep phosphate detectable on a Salifert test running at 5ml vs 10ml for double sensitivity.

If I let phosphate zero out I can see results in less than 48 hours. My rapidly growing digipora start to slow down and their growth nodes get more rounded. I assume this is the coral shifting to stressed calcite formation vs more porous calcium carbonate mode, which may be a clue. Next, the skirts on many of my palys, especially purple deaths start to receed. Birdsnests also start to lose their growth nodes. You can set a watch by this and the speed of changes in corals is shockingly rapid. They improve just as fast. I have a very healthy purple stylo that can tolerate zero phosphate for quit awhile before slowing down. I have a grapefruit size green pocillopora that doesn't care.

I can elevate phosphate via increased feeding, especially reef roids but then my nitrate starts to get out of control. My current regimen keeps nitrate about 10ppm, and dont want to go higher.

I used to keep much bigger tanks and never fussed with phosphate nor cared. With a smaller tank though and that much SPS phosphate is now my #1 parameter to watch.

 

[reef_ninja]

I've been dosing my 20L which has large amounts of fast growing SPS with Seachem Phosphorus. The Seachem product is .5 % phosphorus, and I dose two cap fulls a week to keep phosphate detectable on a Salifert test running at 5ml vs 10ml for double sensitivity.

If I let phosphate zero out I can see results in less than 48 hours. My rapidly growing digipora start to slow down and their growth nodes get more rounded. I assume this is the coral shifting to stressed calcite formation vs more porous calcium carbonate mode, which may be a clue. Next, the skirts on many of my palys, especially purple deaths start to receed. Birdsnests also start to lose their growth nodes. You can set a watch by this and the speed of changes in corals is shockingly rapid. They improve just as fast. I have a very healthy purple stylo that can tolerate zero phosphate for quit awhile before slowing down. I have a grapefruit size green pocillopora that doesn't care.

I can elevate phosphate via increased feeding, especially reef roids but then my nitrate starts to get out of control. My current regimen keeps nitrate about 10ppm, and dont want to go higher.

I used to keep much bigger tanks and never fussed with phosphate nor cared. With a smaller tank though and that much SPS phosphate is now my #1 parameter to watch.

Definitely starting to see some of this in my tank, just not as quickly as you. The only SPS that isn’t ticked off is my birdsnest..... it’s actually looking very nice. My acans and a small button scold are pretty unhappy as well. But the input is great, definitely seeing the impact of nutrients here.

I will add that I don’t get any measurable impact of reef roids on phosphates...... but then again, Randy pointed out that maybe my phosphates were being buffered/binder, and it’s only today that I got measurable po4. So maybe the reef roids impact will change?

 

[reef_ninja]

Update today, nitrates are down to 10 ppm. I'd like to aim to keep them here.

PO4 is down to .25, Ill see if these continue to trend down. I believe Im aiming to keep these at 0.05 to 0.1 ppm.

Hopefully this week with my ability to test throughout the day, and with enough time between doses, I can get somewhat of an idea of what I need to dose.

Im wondering, now that these levels are up, should I consider reducing my feedings a bit? Again, I feed pretty heavy, and I'd really like to not battle the unsightly algae as I had in the past.....

 

[reef_ninja]

Just wanted to keep this going, see it through for now.
Nitrates are holding at about 10 ppm. I’m ok with this, still feeling out the dosing, probably somewhere really small, maybe 2-3 mls per day at most. Seems like a really small dose.

Po4 is now at 0.1, which I’m alright with for now as well. Seems the dose is about 1ml/day, maybe even less. That seems really small to me, but it’s where the numbers are.

Would really like to see some results. About to lose my scoly, it’s going fast. One of my acros is starting to go quickly. Would also be nice to see my acans puffy, but the other LPS (Duncan’s, lobo, frog spawn, chalices) look very good.

 

[ScottB]

@92Miata im feeding about 1.5 cubes and about 2 tsps of pellets per day. I’m also feeding 1/2 tsp reef roids 2-3 times a week. For four fish, it’s definitely heavy, which is why, in my personal experience, I’m not convinced feeding alone is enough to fix the problem. I’ll definitely continue to feed heavy, but I’ll be adding more fish as well.

Great discussion here, not sure about everyone else but I’m taking away a lot from this

That is heavy for four fish, agreed. But only light to moderate for 60G volume.

Everybody join in here... More Fish! More Fish! More...!

 

[amazongb]

I had a similar problem (zero phosphate) and went through the same issue with manual dosing. Corals looked awful.

I decided to use an automated doser and dosed 8ML of Neophos over a 24 hour periods daily, which in my tank is roughly .02 ppm per day. This way, regardless of what my test kit says, I know the tank is getting a steady amount until it can build up. As it started to build up over the course of weeks, the tank kept looking better and better, and I realized that my tank likes phosphates in the higher range of .10 - .20. I even let them creep higher, and the tank just kept looking better. I keep my nitrates on the higher end as well 16-32. There are many ways to keep a reef, high import, high export, or slow and steady, but in the end, it's how the tank and corals look that aid in deciding what to do.

 

[beesnreefs]

This is a great thread. Feel like I'm learning a lot in this conversation.

General question - if the problem is indeed low nitrates/phosphates, is it likely to impact some corals and not others?

In my tank I started seeing a few of my acans and a hammer struggling when my nutrients bottomed out. At the same time, other euphyillia (4 torches) look wonderful and two acan colonies have been puffy and happy. My blastos are all kicking butt. My goni has been cranky. Two trachy's and a button scoly are happy and puffy and I lost a hammer.

 

[reef_ninja]

This is a great thread. Feel like I'm learning a lot in this conversation.

General question - if the problem is indeed low nitrates/phosphates, is it likely to impact some corals and not others?

In my tank I started seeing a few of my acans and a hammer struggling when my nutrients bottomed out. At the same time, other euphyillia (4 torches) look wonderful and two acan colonies have been puffy and happy. My blastos are all kicking butt. My goni has been cranky. Two trachy's and a button scoly are happy and puffy and I lost a hammer.

Great question, I’m wondering the same thing. As I mentioned, the reaction of my corals are mixed. Acans aren’t excited about life, scolys just about done, but my birdsnest is rockin’. Hopefully after a couple more weeks of nutrient stability, we’ll see. Would like to see what others think about your question though.

 

[ScottB]

General question - if the problem is indeed low nitrates/phosphates, is it likely to impact some corals and not others?

Yes, I believe so. Particularly as it relates to PO4. Nitrate consumption by corals is super easy. They don't have to work hard to consume/process. I think of them like carbohydrates as they are processed into energy without a lot of work.

Phosphates are consumed by corals indirectly. The corals capture the bacteria that eat/process PO4. While they need this nutrient, it is harder for them to process.

But each coral has a different level of need and efficiency. Different coral are also more/less efficient at meeting their needs photosynthetically.

Lastly, kinda like us, each coral goes into a given "hunger event" in a different level of overall health and susceptability.

 

[reef_ninja]

Small update. The corals I was concerned about are holding at the “not completely dead yet” phase, but im not sure it’s turning around. We’re back to 0 ppm on the phosphates with dosing 4 mls sodium phosphate solution per night, after letting the po4 drop to .1 or so.

One small ray of light. One night after the po4 was coming down from 1.0 ppm, my scoly had its feeders out. I just gotta get this po4 figured out. Also, the algae’s not really any different, it’s pretty well controlled, so that’s nice.

So for now, I added one more fish, and have my skimmer on a timer so that it runs 20 hours a day. I’m also doubling my dosing of sodium phosphate to 8 mls/night. We’ll see.

 

[Gogo007]

Small update. The corals I was concerned about are holding at the “not completely dead yet” phase, but im not sure it’s turning around. We’re back to 0 ppm on the phosphates with dosing 4 mls sodium phosphate solution per night, after letting the po4 drop to .1 or so.

One small ray of light. One night after the po4 was coming down from 1.0 ppm, my scoly had its feeders out. I just gotta get this po4 figured out. Also, the algae’s not really any different, it’s pretty well controlled, so that’s nice.

So for now, I added one more fish, and have my skimmer on a timer so that it runs 20 hours a day. I’m also doubling my dosing of sodium phosphate to 8 mls/night. We’ll see.

Good please keep us updated i would like to know the end result