Rock absorbing nutrients?

[GJW]

Long story short, after some neglect my 14 gallon had a severe bubble algae outbreak and I decided to re-scape entirely with dry rock (Tropic Eden). This seemed to worsen my pre-existing dino issue (ostreopsis) so I decided to test more regularly. I quickly realized that both my nitrates and phosphates were at 0. Along with feeding, I have been dosing NeoNitro and NeoPhos daily for over a month now and it has been very difficult to raise these values. My nitrates seem so respond however it tends to drop around 1-2 ppm each day. It is very difficult to get my phosphates over 0, even dosing 10 ml which seems like a lot. My best guess is the rock is absorbing these nutrients, and I am looking for some guidance as it seems to be fueling the dinos (UV doesn't seem to be helping). I do about a 5% water change each week to get them off the sand bed. Thankfully the corals look great and are growing.

 

[EnterName]

There is an ongoing equilibrium reaction that binds and dissolves phosphate to/from calcium carbonate (your rockscape and substrate). If your rocks are not sufficiently saturated, more phosphate will be bound than dissolved, so your tests will show 0ppm, especially if they aren't very precise. Once the rocks are sufficiently saturated, phosphate can rise. For the same reason, water changes tend to be quite inefficient when trying to reduce phosphate levels, because buffered phosphate will just redissolve.
To save a few bucks, I recommend using a DIY recipe to dose phosphate and slowly saturate the calcium carbonate: https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/
This can take quite a while. I remember dumping insane amounts of phosphate into my tank until phosphate started to become detectable.

If nitrate is also an issue, I recommend dosing ammonia in frequent but small batches instead of supplying nitrate directly: https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
Ammonia is the preferred nitrogen source for corals, algae, and bacteria, as nitrate has to be converted back to ammonia first before these organisms can get to the precious nitrogen they actually want (there may be a few exceptions to this rule). This conversion requires energy and precious trace elements that can limit the actual nitrogen uptake.

Of course, you will also have a lot of biomass forming as dinoflagellates, biofilms, and algae grow, so a lot of those nutrients will be bound to biomass and therefore no longer detectable by your tests. Once all surface area is overgrown and the population of all sorts of organisms has reached a peak, you may be able to see nutrients increase as other elements/molecules become the limiting factor. Carbon, for example, can be a limiting factor, so people use "carbon dosing" (adding alcohol or acetic acid) to encourage bacteria growth. Iron is also a very common limiting factor because it is needed for many processes in a reef tank, but the actual concentrations of it are very low in natural sea water.

When starting a tank with dry rock (my current system, running for 6+ years now, was started with 100% dry rock and substrate), it is fairly common to have very low nutrients for a long time. That's why I'm dosing ammonia and phosphate multiple times daily to maintain stable nutrient levels. It's a bit difficult at first, but after a while you get to know your tank and see how nutrients will react in relation to each other. It makes it easy to maintain nutrient levels within your preferred target ranges once you get the hang of it, and I prefer it over having to constantly try to keep them down.

If Dinoflagellates are a symptom or the cause of low nutrient levels is a bit controversial, so some people recommend dosing nutrients to get rid of them while others say dosing nutrients will just feed them. I think both things can be true, so you should just try it out :)

 

[Randy Holmes-Farley Verified Community Expert]

Short story on nitrate is that no rocks bind it.

 

[GJW]

There is an ongoing equilibrium reaction that binds and dissolves phosphate to/from calcium carbonate (your rockscape and substrate). If your rocks are not sufficiently saturated, more phosphate will be bound than dissolved, so your tests will show 0ppm, especially if they aren't very precise. Once the rocks are sufficiently saturated, phosphate can rise. For the same reason, water changes tend to be quite inefficient when trying to reduce phosphate levels, because buffered phosphate will just redissolve.
To save a few bucks, I recommend using a DIY recipe to dose phosphate and slowly saturate the calcium carbonate: https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/
This can take quite a while. I remember dumping insane amounts of phosphate into my tank until phosphate started to become detectable.

If nitrate is also an issue, I recommend dosing ammonia in frequent but small batches instead of supplying nitrate directly: https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
Ammonia is the preferred nitrogen source for corals, algae, and bacteria, as nitrate has to be converted back to ammonia first before these organisms can get to the precious nitrogen they actually want (there may be a few exceptions to this rule). This conversion requires energy and precious trace elements that can limit the actual nitrogen uptake.

Of course, you will also have a lot of biomass forming as dinoflagellates, biofilms, and algae grow, so a lot of those nutrients will be bound to biomass and therefore no longer detectable by your tests. Once all surface area is overgrown and the population of all sorts of organisms has reached a peak, you may be able to see nutrients increase as other elements/molecules become the limiting factor. Carbon, for example, can be a limiting factor, so people use "carbon dosing" (adding alcohol or acetic acid) to encourage bacteria growth. Iron is also a very common limiting factor because it is needed for many processes in a reef tank, but the actual concentrations of it are very low in natural sea water.

When starting a tank with dry rock (my current system, running for 6+ years now, was started with 100% dry rock and substrate), it is fairly common to have very low nutrients for a long time. That's why I'm dosing ammonia and phosphate multiple times daily to maintain stable nutrient levels. It's a bit difficult at first, but after a while you get to know your tank and see how nutrients will react in relation to each other. It makes it easy to maintain nutrient levels within your preferred target ranges once you get the hang of it, and I prefer it over having to constantly try to keep them down.

If Dinoflagellates are a symptom or the cause of low nutrient levels is a bit controversial, so some people recommend dosing nutrients to get rid of them while others say dosing nutrients will just feed them. I think both things can be true, so you should just try it out :)

This is very informative and helpful thank you!

 

[Fish Fan]

There is an ongoing equilibrium reaction that binds and dissolves phosphate to/from calcium carbonate (your rockscape and substrate). If your rocks are not sufficiently saturated, more phosphate will be bound than dissolved, so your tests will show 0ppm, especially if they aren't very precise. Once the rocks are sufficiently saturated, phosphate can rise. For the same reason, water changes tend to be quite inefficient when trying to reduce phosphate levels, because buffered phosphate will just redissolve.
To save a few bucks, I recommend using a DIY recipe to dose phosphate and slowly saturate the calcium carbonate: https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/
This can take quite a while. I remember dumping insane amounts of phosphate into my tank until phosphate started to become detectable.

If nitrate is also an issue, I recommend dosing ammonia in frequent but small batches instead of supplying nitrate directly: https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
Ammonia is the preferred nitrogen source for corals, algae, and bacteria, as nitrate has to be converted back to ammonia first before these organisms can get to the precious nitrogen they actually want (there may be a few exceptions to this rule). This conversion requires energy and precious trace elements that can limit the actual nitrogen uptake.

Of course, you will also have a lot of biomass forming as dinoflagellates, biofilms, and algae grow, so a lot of those nutrients will be bound to biomass and therefore no longer detectable by your tests. Once all surface area is overgrown and the population of all sorts of organisms has reached a peak, you may be able to see nutrients increase as other elements/molecules become the limiting factor. Carbon, for example, can be a limiting factor, so people use "carbon dosing" (adding alcohol or acetic acid) to encourage bacteria growth. Iron is also a very common limiting factor because it is needed for many processes in a reef tank, but the actual concentrations of it are very low in natural sea water.

When starting a tank with dry rock (my current system, running for 6+ years now, was started with 100% dry rock and substrate), it is fairly common to have very low nutrients for a long time. That's why I'm dosing ammonia and phosphate multiple times daily to maintain stable nutrient levels. It's a bit difficult at first, but after a while you get to know your tank and see how nutrients will react in relation to each other. It makes it easy to maintain nutrient levels within your preferred target ranges once you get the hang of it, and I prefer it over having to constantly try to keep them down.

If Dinoflagellates are a symptom or the cause of low nutrient levels is a bit controversial, so some people recommend dosing nutrients to get rid of them while others say dosing nutrients will just feed them. I think both things can be true, so you should just try it out :)

Look at you now with the well written, helpful reply

 

[Dan_P]

There is an ongoing equilibrium reaction that binds and dissolves phosphate to/from calcium carbonate (your rockscape and substrate). If your rocks are not sufficiently saturated, more phosphate will be bound than dissolved, so your tests will show 0ppm, especially if they aren't very precise. Once the rocks are sufficiently saturated, phosphate can rise. For the same reason, water changes tend to be quite inefficient when trying to reduce phosphate levels, because buffered phosphate will just redissolve.
To save a few bucks, I recommend using a DIY recipe to dose phosphate and slowly saturate the calcium carbonate: https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/
This can take quite a while. I remember dumping insane amounts of phosphate into my tank until phosphate started to become detectable.

If nitrate is also an issue, I recommend dosing ammonia in frequent but small batches instead of supplying nitrate directly: https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
Ammonia is the preferred nitrogen source for corals, algae, and bacteria, as nitrate has to be converted back to ammonia first before these organisms can get to the precious nitrogen they actually want (there may be a few exceptions to this rule). This conversion requires energy and precious trace elements that can limit the actual nitrogen uptake.

Of course, you will also have a lot of biomass forming as dinoflagellates, biofilms, and algae grow, so a lot of those nutrients will be bound to biomass and therefore no longer detectable by your tests. Once all surface area is overgrown and the population of all sorts of organisms has reached a peak, you may be able to see nutrients increase as other elements/molecules become the limiting factor. Carbon, for example, can be a limiting factor, so people use "carbon dosing" (adding alcohol or acetic acid) to encourage bacteria growth. Iron is also a very common limiting factor because it is needed for many processes in a reef tank, but the actual concentrations of it are very low in natural sea water.

When starting a tank with dry rock (my current system, running for 6+ years now, was started with 100% dry rock and substrate), it is fairly common to have very low nutrients for a long time. That's why I'm dosing ammonia and phosphate multiple times daily to maintain stable nutrient levels. It's a bit difficult at first, but after a while you get to know your tank and see how nutrients will react in relation to each other. It makes it easy to maintain nutrient levels within your preferred target ranges once you get the hang of it, and I prefer it over having to constantly try to keep them down.

If Dinoflagellates are a symptom or the cause of low nutrient levels is a bit controversial, so some people recommend dosing nutrients to get rid of them while others say dosing nutrients will just feed them. I think both things can be true, so you should just try it out :)

Why aren’t we routinely pre-saturating dry rock and new aragonite sand with phosphate to minimize phosphate depletion in new aquaria?

 

[EnterName]

There is an ongoing equilibrium reaction that binds and dissolves phosphate to/from calcium carbonate (your rockscape and substrate). If your rocks are not sufficiently saturated, more phosphate will be bound than dissolved, so your tests will show 0ppm, especially if they aren't very precise. Once the rocks are sufficiently saturated, phosphate can rise. For the same reason, water changes tend to be quite inefficient when trying to reduce phosphate levels, because buffered phosphate will just redissolve.
To save a few bucks, I recommend using a DIY recipe to dose phosphate and slowly saturate the calcium carbonate: https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/
This can take quite a while. I remember dumping insane amounts of phosphate into my tank until phosphate started to become detectable.

If nitrate is also an issue, I recommend dosing ammonia in frequent but small batches instead of supplying nitrate directly: https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
Ammonia is the preferred nitrogen source for corals, algae, and bacteria, as nitrate has to be converted back to ammonia first before these organisms can get to the precious nitrogen they actually want (there may be a few exceptions to this rule). This conversion requires energy and precious trace elements that can limit the actual nitrogen uptake.

Of course, you will also have a lot of biomass forming as dinoflagellates, biofilms, and algae grow, so a lot of those nutrients will be bound to biomass and therefore no longer detectable by your tests. Once all surface area is overgrown and the population of all sorts of organisms has reached a peak, you may be able to see nutrients increase as other elements/molecules become the limiting factor. Carbon, for example, can be a limiting factor, so people use "carbon dosing" (adding alcohol or acetic acid) to encourage bacteria growth. Iron is also a very common limiting factor because it is needed for many processes in a reef tank, but the actual concentrations of it are very low in natural sea water.

When starting a tank with dry rock (my current system, running for 6+ years now, was started with 100% dry rock and substrate), it is fairly common to have very low nutrients for a long time. That's why I'm dosing ammonia and phosphate multiple times daily to maintain stable nutrient levels. It's a bit difficult at first, but after a while you get to know your tank and see how nutrients will react in relation to each other. It makes it easy to maintain nutrient levels within your preferred target ranges once you get the hang of it, and I prefer it over having to constantly try to keep them down.

If Dinoflagellates are a symptom or the cause of low nutrient levels is a bit controversial, so some people recommend dosing nutrients to get rid of them while others say dosing nutrients will just feed them. I think both things can be true, so you should just try it out :)

Why aren’t we routinely pre-saturating dry rock and new aragonite sand with phosphate to minimize phosphate depletion in new aquaria?

I actually tried testing how much phosphate I would need to do this for my substrate but testing it turned out more complex than anticipated because you will need to keep a stable pH in the test vessel and would probably also need some water movement so deeper substrate layers get into more contact with phosphate. In my (apparently quite badly) applied tests the pH dropped and phosphate even increased in the control sample.

I talked about this in Jonas' phosphate binding kinetics experiment which was very interesting to me at the time as my tank migration was still pending and I was worried to drop phosphate too much when replacing the substrate.
(https://www.reef2reef.com/threads/results-from-my-home-study-phosphate-binding-kinetics.1138371/)

In the end I opted to add sand in 1-2L batches which sometimes still drops my ultra low nutrient system below detectable levels, but it's easy to control and counter with a DIY monosodium phosphate solution.

 

[Dan_P]

I actually tried testing how much phosphate I would need to do this for my substrate but testing it turned out more complex than anticipated because you will need to keep a stable pH in the test vessel and would probably also need some water movement so deeper substrate layers get into more contact with phosphate. In my (apparently quite badly) applied tests the pH dropped and phosphate even increased in the control sample.

I talked about this in Jonas' phosphate binding kinetics experiment which was very interesting to me at the time as my tank migration was still pending and I was worried to drop phosphate too much when replacing the substrate.
(https://www.reef2reef.com/threads/results-from-my-home-study-phosphate-binding-kinetics.1138371/)

In the end I opted to add sand in 1-2L batches which sometimes still drops my ultra low nutrient system below detectable levels, but it's easy to control and counter with a DIY monosodium phosphate solution.

My recent experience with two small experimental aquaria with aragnite sand bottoms went smoothly based on the kinetics of PO4 adsorption. I followed the daily rate of PO4 decline after each dose and observed rapid adsorption stopped after a few days. After this, the adsorption rate settled down to adsorption requiring days rather than hours to deplete the PO4. I did not bother monitoring pH or temperature. My goal was to keep PO4 between 0.05 and 0.1 ppm for several days to make sure that the daily PO4 depletion in the experiment was caused by the photosynthetic organisms not the sand. I performed a parallel study of ammonia consumption before turning on the lights to understand ammonia consumption rates by nitrifying bacteria in the dark.

 

[EnterName]

I actually tried testing how much phosphate I would need to do this for my substrate but testing it turned out more complex than anticipated because you will need to keep a stable pH in the test vessel and would probably also need some water movement so deeper substrate layers get into more contact with phosphate. In my (apparently quite badly) applied tests the pH dropped and phosphate even increased in the control sample.

I talked about this in Jonas' phosphate binding kinetics experiment which was very interesting to me at the time as my tank migration was still pending and I was worried to drop phosphate too much when replacing the substrate.
(https://www.reef2reef.com/threads/results-from-my-home-study-phosphate-binding-kinetics.1138371/)

In the end I opted to add sand in 1-2L batches which sometimes still drops my ultra low nutrient system below detectable levels, but it's easy to control and counter with a DIY monosodium phosphate solution.

My recent experience with two small experimental aquaria with aragnite sand bottoms went smoothly based on the kinetics of PO4 adsorption. I followed the daily rate of PO4 decline after each dose and observed rapid adsorption stopped after a few days. After this, the adsorption rate settled down to adsorption requiring days rather than hours to deplete the PO4. I did not bother monitoring pH or temperature. My goal was to keep PO4 between 0.05 and 0.1 ppm for several days to make sure that the daily PO4 depletion in the experiment was caused by the photosynthetic organisms not the sand. I performed a parallel study of ammonia consumption before turning on the lights to understand ammonia consumption rates by nitrifying bacteria in the dark.

Okay, I think I understand, but maybe we had different goals.

Let's say you have a running tank without substrate and a known PO4 level. And you wanted to fill that tank with x kilograms of your substrate. Would you be able to predict the PO4 adsorption/binding based on that? Or, could you create a phosphate solution to soak the substrate in, so it would have a minimal effect on the PO4 levels of the tank?

That was my initial goal, but it turned out to be difficult to approximate especially when testing in very small Jars.
In the end, I didn't go the fancy "math/chemistry" way and instead opted for the "engineering" way by simply adding substrate in batches and countering the measured delta in phosphate levels each day by dosing It gets the job done, but is less elegant

I still dropped to undetectable levels a few times (and still occasionally do when adding more)... Some dinos appeared but dosing nutrients and getting all trace elements back into order according to an ICP-MS test fixed the issue quite fast... Oddly enough Strontium appeared to make the difference for the dinos in the end, but I think that was pure coincidence

Have you published any of those studies here on R2R yet? Would be an interesting read

 

[Fish Fan]

Why aren’t we routinely pre-saturating dry rock and new aragonite sand with phosphate to minimize phosphate depletion in new aquaria?

I believe there are many who do this while they are cycling dry rock in a Brute can or similar. Or conversely, they are stripping off excess phosphate leaching from rocks before placing them in a tank. I wish I had done that with the dry rock I have now, which is acting like a sponge for phosphate.

 

[EnterName]

I believe there are many who do this while they are cycling dry rock in a Brute can or similar. Or conversely, they are stripping off excess phosphate leaching from rocks before placing them in a tank. I wish I had done that with the dry rock I have now, which is acting like a sponge for phosphate.

I had to add so much phosphate when I started my current system. 100% dry rock and substrate... I added a few ppm phosphate a day for weeks just for it to "disappear" within a few hours. The equilibrium reaction seems to be quite fast and it's really difficult to find the right spot so you don't accidentally overshoot and then end up having to reduce phosphate again

I like having low phosphate levels since it's far easier to add than to remove, and corals are used to very low phosphate levels in the ocean, so an actual limitation seems rare. It's only when I add a lot of new substrate or acid-cured rock at once that I see them become unhappy when phosphate drops to undetectable levels.

 

[Fish Fan]

I had to add so much phosphate when I started my current system. 100% dry rock and substrate... I added a few ppm phosphate a day for weeks just for it to "disappear" within a few hours. The equilibrium reaction seems to be quite fast and it's really difficult to find the right spot so you don't accidentally overshoot and then end up having to reduce phosphate again

I like having low phosphate levels since it's far easier to add than to remove, and corals are used to very low phosphate levels in the ocean, so an actual limitation seems rare. It's only when I add a lot of new substrate or acid-cured rock at once that I see them become unhappy when phosphate drops to undetectable levels.

I realized that one way or another I've always used real wet rock, either from someone else's system, or from a fish store, or more recently the ocean maricultured stuff from the Gulf of Mexico here in the US. This most recent tank I've started is bare bottom and dry rock, and this will be my first and last dry rock/bare bottom start! The tank has been nothing but problems, the phosphate bottoms right out if I don't dose it.

Last summer I went out of town for a week, and did not dose phosphate in that time and came home to brown sludge covering everything

 

[GJW]

I realized that one way or another I've always used real wet rock, either from someone else's system, or from a fish store, or more recently the ocean maricultured stuff from the Gulf of Mexico here in the US. This most recent tank I've started is bare bottom and dry rock, and this will be my first and last dry rock/bare bottom start! The tank has been nothing but problems, the phosphate bottoms right out if I don't dose it.

Last summer I went out of town for a week, and did not dose phosphate in that time and came home to brown sludge covering everything

I think with my next build I will do half live/dry rock.

 

[Randy Holmes-Farley Verified Community Expert]

If I used dry rock that had a deficit of phosphate (some have excess) then I might well precook it to my desired target.

 

[Fish Fan]

If I used dry rock that had a deficit of phosphate (some have excess) then I might well precook it to my desired target.

If I had thought of this, I would have done it myself

If cycling dry rocks in a Brute, and if they were soaking up all the phosphate, would there be any reason not to add a rather massive amount of phosphate in the hope of reaching an equilibrium faster, or does it not work that way?

Thank you for your help!

 

[Randy Holmes-Farley Verified Community Expert]

I think an iterative dose and measure approach would work best. It takes a lot, but one could also substantially overshoot and then be stuck over target.


It can keep on absorbing more and more if the amount in the water is sufficient. Then it could release that later when you try to keep it lower.

 

[Fish Fan]

I think an iterative dose and measure approach would work best. It takes a lot, but one could also substantially overshoot and then be stuck over target.


It can keep on absorbing more and more if the amount in the water is sufficient. Then it could release that later when you try to keep it lower.

Thank you!

I was asking because I have been manually dosing a small amount daily in a running tank for many months now, it would be great if it would finally hit that equilibrium

 

[Randy Holmes-Farley Verified Community Expert]

I’d at least dose the upper end of your target range if it keeps sucking it up. Then the worst that would happen is it stays near the upper end.

 

[Fish Fan]

I’d at least dose the upper end of your target range if it keeps sucking it up. Then the worst that would happen is it stays near the upper end.

Great, thank you again!

 

[EnterName]

When starting a tank with lots of dry rock, the phosphate will probably be depleted by the ugly phase, so I don't know if this approach even works as well as we are making it sound.
I mean... I tried it, and had too much phosphate for a short while, but then the green hair algae just ate it all up.

Of course the phosphate doesn't simply disappear, it's just bound to the algae, but as it broke down again, the skimmer took care of it, and all sorts of biofilm or whatever establishes during that time will bind lots of it as well.
I could imagine it's better than doing nothing, but I feel like the pre-saturation method works better for small rockscape adjustments in low nutrient systems, during tank upgrades, or when adding substrate to an already running system where you don't have to expect a severe ugly phase.