Experiment: phosphate in rocks

[NanJ]

To "test" the theory of phosphates leaching out of rock, I put a rock from the DT into a bucket of saltwater taken from the auto-water change reservoir tank.

-- AWC saltwater phosphate read 0.09 ppm with Hanna Checker. (Pretty high for "plain" saltwater.....need to figure that part out.)
-- About 3/4 gallon AWC saltwater in a bucket.
-- Added a rock from the DT that was about 5-6" in diameter.
-- Phosphates 4 days later read 0.38 ppm.
-- Phosphates 4 days later read 0.54 ppm

This was not a very controlled experiment but I think it does show phosphates leach out of rocks. We are considering an algae scrubber and I wanted to verify the information I was given that rocks are a reservoir for phosphates. I assume that the pH of the water in the bucket changed over the week and impacted the phosphates leaching out of the rock. Like I said, it wasn't a controlled experiment!

The phosphates in our tank consistently run 0.35-0.40 ppm and we have to scrub patches of hair algae on the rocks each week to stay ahead of the algae. We are hoping an algae scrubber will help "get our hands out of the tank".

Shared this information just to add to the knowledge base.

 

[Lavey29]

Thanks for sharing, .35 to .4 is elevated but not overly high. How do your corals look? Many successful tanks operate in this range including mine.

 

[Garf]

To "test" the theory of phosphates leaching out of rock, I put a rock from the DT into a bucket of saltwater taken from the auto-water change reservoir tank.

-- AWC saltwater phosphate read 0.09 ppm with Hanna Checker. (Pretty high for "plain" saltwater.....need to figure that part out.)
-- About 3/4 gallon AWC saltwater in a bucket.
-- Added a rock from the DT that was about 5-6" in diameter.
-- Phosphates 4 days later read 0.38 ppm.
-- Phosphates 4 days later read 0.54 ppm

This was not a very controlled experiment but I think it does show phosphates leach out of rocks. We are considering an algae scrubber and I wanted to verify the information I was given that rocks are a reservoir for phosphates. I assume that the pH of the water in the bucket changed over the week and impacted the phosphates leaching out of the rock. Like I said, it wasn't a controlled experiment!

The phosphates in our tank consistently run 0.35-0.40 ppm and we have to scrub patches of hair algae on the rocks each week to stay ahead of the algae. We are hoping an algae scrubber will help "get our hands out of the tank".

Shared this information just to add to the knowledge base.

What are your nitrates at?

 

[Dan_P]

To "test" the theory of phosphates leaching out of rock, I put a rock from the DT into a bucket of saltwater taken from the auto-water change reservoir tank.

-- AWC saltwater phosphate read 0.09 ppm with Hanna Checker. (Pretty high for "plain" saltwater.....need to figure that part out.)
-- About 3/4 gallon AWC saltwater in a bucket.
-- Added a rock from the DT that was about 5-6" in diameter.
-- Phosphates 4 days later read 0.38 ppm.
-- Phosphates 4 days later read 0.54 ppm

This was not a very controlled experiment but I think it does show phosphates leach out of rocks. We are considering an algae scrubber and I wanted to verify the information I was given that rocks are a reservoir for phosphates. I assume that the pH of the water in the bucket changed over the week and impacted the phosphates leaching out of the rock. Like I said, it wasn't a controlled experiment!

The phosphates in our tank consistently run 0.35-0.40 ppm and we have to scrub patches of hair algae on the rocks each week to stay ahead of the algae. We are hoping an algae scrubber will help "get our hands out of the tank".

Shared this information just to add to the knowledge base.

Thanks for sharing.

Good luck with algae control.

 

[Randy Holmes-Farley]

FYI, the same reversible binding happens with almost any type of binding to a mineral surface (e.g., GFO) or a polymer material, with the exception of certain organics such as some proteins on GAC that may distort their structure in a way that just won’t go back.

 

[NanJ]

FYI, the same reversible binding happens with almost any type of binding to a mineral surface (e.g., GFO) or a polymer material, with the exception of certain organics such as some proteins on GAC that may distort their structure in a way that just won’t go back.

Does that mean the phosphate concentration reaches an equilibrium with the media such as Phosgard by Seachem that is supposed to remove it from the water?

 

[NanJ]

What are your nitrates at?

20-25 ppm

 

[NanJ]

Thanks for sharing, .35 to .4 is elevated but not overly high. How do your corals look? Many successful tanks operate in this range including mine.

I read that it is certainly possible to have a thriving tank with phosphates above the generally accepted levels. I think our corals are okay but seem to grow slowly - but then I don’t know how to evaluate growth rate. Guess it depends, too, on the species.

Our main reason to be adding an algae scrubber is to decrease unwanted algae growth in the DT. My husband’s health is iffy and when something happens with him the tank gets minimal attention. When he is able to get back to it, we have to scrub the rocks weekly to beat down the algae growth. If my dream comes true, an algae scrubber will help with this situation.

 

[Lavey29]

I read that it is certainly possible to have a thriving tank with phosphates above the generally accepted levels. I think our corals are okay but seem to grow slowly - but then I don’t know how to evaluate growth rate. Guess it depends, too, on the species.

Our main reason to be adding an algae scrubber is to decrease unwanted algae growth in the DT. My husband’s health is iffy and when something happens with him the tank gets minimal attention. When he is able to get back to it, we have to scrub the rocks weekly to beat down the algae growth. If my dream comes true, an algae scrubber will help with this situation.

Well certainly try different tools of the hobb6 to see if they make tank maintenance easier for you. I have found that the less devices I rely on the easier it is for me personally but each tank is unique. With scrubbers you just need to watch nutrients levels so they don't 0 out on you but lots of people use them effectively for their tanks....good luck

 

[Randy Holmes-Farley]

Does that mean the phosphate concentration reaches an equilibrium with the media such as Phosgard by Seachem that is supposed to remove it from the water?

Yes.

If you leave it in place and start to lower phosphate, some will come back off.

I have demonstrated that myself with GFO, and aluminum oxide will behave similarly.


That said, I do not know what concentration ranges these effects are greatest for aluminum oxide.

 

[KStatefan]

I read that it is certainly possible to have a thriving tank with phosphates above the generally accepted levels. I think our corals are okay but seem to grow slowly - but then I don’t know how to evaluate growth rate. Guess it depends, too, on the species.

Our main reason to be adding an algae scrubber is to decrease unwanted algae growth in the DT. My husband’s health is iffy and when something happens with him the tank gets minimal attention. When he is able to get back to it, we have to scrub the rocks weekly to beat down the algae growth. If my dream comes true, an algae scrubber will help with this situation.

I have not had that experience with my algae scrubber. I still have to scrub surfaces in the tank weekly and now clean the scrubber every two weeks.

 

[NanJ]

I have not had that experience with my algae scrubber. I still have to scrub surfaces in the tank weekly and now clean the scrubber every two weeks.

Well, that is discouraging for my plan!

As I understand algae scrubbers, the light supply has to be pretty powerful to outcompete algae in the tank. Because algae scrubbers are so expensive and sometimes due to space limitations, people often undersize them for the amount of load (phosphate-saturated rocks, fish feeding/waste) they are up against . I am not saying that is your situation, just relating what I have learned.

 

[jda]

I did an experiment and more than 50 ppm of po4 bound to .16, or so in half of a Phosban reactor of aragonite in a 10g tank. The aragonite can hold a lot. It also can come back off.

There is no actual evidence that a ATS algae can outcompete algae in a tank under any conditions where a reef would survive. I know that a few members seem to think so, but it does not happen. The ATS is just another place where algae can grow uninterrupted (no consumers) and is easy to harvest - no more. If you don't have enough consumers in your display tank, then it becomes an ATS or refuge too.

 

[exnisstech]

Well, that is discouraging for my plan!

As I understand algae scrubbers, the light supply has to be pretty powerful to outcompete algae in the tank. Because algae scrubbers are so expensive and sometimes due to space limitations, people often undersize them for the amount of load (phosphate-saturated rocks, fish feeding/waste) they are up against . I am not saying that is your situation, just relating what I have learned.

I've read several threads lately that more or less turn into arguments about ATS. People that love them say they do exactly what you would like one to do, grow algae so it doesn't grow in the display. I do not want to pull him into an argument but maybe reach out to @VintageReefer. He runs one successfully and seems more than willing to share knowledge. I don't think he would mind conversing via DM to avoid having to keep defending his results. I have not used one so I do not have an oppinion. That said I've been doing this long enough to know that just because something doesn't work for one person doesn't mean it won't work for someone else. I say go for the ATS and see if it works for you.

 

[Quietman]

My experience with my ATS (Santa Monica Rain2) on my tank was and is a positive one with respect to algae control. In my case it's not a magic bullet and there's still algae which is mostly GHA now. My tank has run 3/.03 N/P almost from the beginning but always had a GHA problem. What I've noticed is with the ATS running, the algae growth pattern changed. It used to grow on any exposed rock surface and was a very difficult to remove both manually and for any clean up crew. After the ATS was established the algae became much easier to remove from the rock and once removed took considerable time to grow back if at all.

After more than a year, I still have GHA but it grows now mostly on the sand bed and a few locations where I believe the rhizomes lodged under the rock surface. Even this simply a tug and it comes off situation. Much, much easier to clean the tank mostly just using a hose draining into a sock in the sump. Getting up in years myself, this has been much easier to maintain.

pH also doesn't drop as low, but was always above 7.8 so never really an issue I was tracking.

 

[NanJ]

I've read several threads lately that more or less turn into arguments about ATS. People that love them say they do exactly what you would like one to do, grow algae so it doesn't grow in the display. I do not want to pull him into an argument but maybe reach out to @VintageReefer. He runs one successfully and seems more than willing to share knowledge. I don't think he would mind conversing via DM to avoid having to keep defending his results. I have not used one so I do not have an oppinion. That said I've been doing this long enough to know that just because something doesn't work for one person doesn't mean it won't work for someone else. I say go for the ATS and see if it works for you.

Yes, I have followed those threads and they did, uh, devolve...
And I completely agree that what works for one tank may not work for another. We are going to give it a shot and hope for the best.

 

[NanJ]

My experience with my ATS (Santa Monica Rain2) on my tank was and is a positive one with respect to algae control. In my case it's not a magic bullet and there's still algae which is mostly GHA now. My tank has run 3/.03 N/P almost from the beginning but always had a GHA problem. What I've noticed is with the ATS running, the algae growth pattern changed. It used to grow on any exposed rock surface and was a very difficult to remove both manually and for any clean up crew. After the ATS was established the algae became much easier to remove from the rock and once removed took considerable time to grow back if at all.

After more than a year, I still have GHA but it grows now mostly on the sand bed and a few locations where I believe the rhizomes lodged under the rock surface. Even this simply a tug and it comes off situation. Much, much easier to clean the tank mostly just using a hose draining into a sock in the sump. Getting up in years myself, this has been much easier to maintain.

pH also doesn't drop as low, but was always above 7.8 so never really an issue I was tracking.

Thank you for sharing your positive experience. Your tank's N & P within desirable parameters, an algae scrubber - and still some tolerable algae issues. It goes to show there is no easy answer. We are not looking for a magic bullet, just something to make care a bit more manageable.

 

[jda]

This is technical, but it might help in your quest. po4 does not leach out of rock. It unbinds. This might seem the same, but binding has rules and is predictable. The more than you raise po4 in the water, the more the rock/sand binds. The rock and sand will not just release/leach po4 - you have to lower the water column level of po4 for the rock/sand to unbind.

This is a bind and unbind type of deal, not absorb and leach. You can plan an approach to this and the results will follow.

Growing algae will have rules too. Pay attention to the people with their own chemistry forums and folks who have run some of the largest captive reefs on the planet... you cannot remove algae from one place by growing algae in another. Period. Step up your algae consumers in the tank and if you do grow algae in other places without consumers, your waste products can be lower. Usually there are easy answers, just people who do not know how to read them. Please spend a bit on algae consumers or not much will change.

 

[NanJ]

I did an experiment and more than 50 ppm of po4 bound to .16, or so in half of a Phosban reactor of aragonite in a 10g tank. The aragonite can hold a lot. It also can come back off.

There is no actual evidence that a ATS algae can outcompete algae in a tank under any conditions where a reef would survive. I know that a few members seem to think so, but it does not happen. The ATS is just another place where algae can grow uninterrupted (no consumers) and is easy to harvest - no more. If you don't have enough consumers in your display tank, then it becomes an ATS or refuge too.

Interesting experiment. I had never thought of the phosphate coming off until Randy replied in this thread. In my innocence, I thought if a product claims to remove phosphate then, logically, it wouldn't let it come back off!

We try to maintain numerous and a variety of consumers such as snails, hermits, shrimp, crabs, conchs, Tangs. In our experience these do not eat GHA once it gets some length to it.

 

[jda]

The products remove po4 from the water. The rock/sand then unbinds some. You have to wash, rinse repeat this for a long time to remove all of the po4 from the rocks. ALWAYS change your GFO or Aluminum Oxide when you change water or else po4 can unbind from these too.

Not many consumers will want to eat GHA until there is no other choice. Some urchins like rock, pencil and tuxedos will stay on the rocks, but other snails will wander off to the glass to eat the easy algae. You just have to get more of them until they have no choice - sometimes this means hundreds of snails and a dozen or more urchins. If you see these things in algae patches in the ocean, they are in high numbers. Urchin packs from Reeftopia are not too expensive. Siphon over the top of the algae helps them out a lot - you can let the algae settle to the bottom and pour most of the water in the bucket back in.