Phosphate flow out of rocks

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Phosphate flow out of live rock

Many people, when they finally get very low nutrients for the first time, worry when more (not less) algae starts to grow on their rocks. It seems really strange, especially when nitrate and phosphate tests have been lower than before. What is happening is that phosphate is coming out of the rocks. Remember, phosphate is invisible, so you can only see the effects of it, and it always "flows" from higher concentrations to lower concentrations (just like heat does).

Example: If your room is warm, and you put a cold object on the floor, heat from the air in the room will "flow" into the object until the object and the air are the same temperature. Example 2: If you put a hot object on the floor, heat will "flow" out of the object and go into the air in the room, again, until the air and the object are the same temperature. Now suppose you open your windows (in the winter). The warm air in your room will go out the windows, and it will get colder in the room. The object on the floor is now warmer than the air, so heat will flow out of the object and into the air, and then out the window.

Think of phosphate as the heat, and your rocks as the object. As you filter out phosphate from the water, the phosphate level in the water drops. Now, since the phosphate level in the water is lower than the phosphate level in the rocks, phosphate flows from the rocks into the water, and then from the water into your filter. This continues until the phosphate levels in the rocks and water are level again. And remember, you can't see this invisible flow. It's like a fast flowing, but shallow, river. And it can be much more phosphate than how much you are feeding each day.

This flow causes an interesting thing to happen. As the phosphate comes out of the rocks, it then becomes available to feed algae as soon as the phosphate reaches the surface of the rocks where there is light. So, since the surface of the rocks is rough and has light, it starts growing MORE algae there (not less) as the phosphate comes out of the rocks. This is a pretty amazing thing to see for the first time, because if you did not know what was happening you would probably think that your filters are not working. Here are the signs of phosphate coming out of the rocks:

1. The rocks are older, and have slowly developed algae problems in the past year.

2. Your filtering is new, maybe only a few months old.

3. Nitrate and phosphate measurements in the water are low, usually the lowest they have been in a long time.

4. Green hair algae (not brown) on the rocks has increased in certain spots, usually on corners and protrusions at the top.

5. The glass has not needed cleaning as much.


Most people have never seen the effects of large amounts of phosphate coming out of the rocks quickly. But sure enough, it can. How long does it continue? For 2 months to 6 months, depending on how much phosphate is in the rocks, how strong your filtering is, and how many other phosphate-removing filters you have (GFO, carbon dosing, etc). But one day you will see patches of white rock that were covered in green hair the day before; this is a sure sign that the algae are losing their phosphate supply from the rocks and can no longer hold on. Now it's just a matter of days before the rocks are clear.

 

[BryanM]

So I have battled high phos for a long time. GFO does work, but I have this issue where when I get it down to a reasonable level (.1-.3), i stop GFO, and it just goes back up.

I just wonder when I might every see this stabilize.

I do not have algae issues on any rocks.

 

[Bear22]

Any solid scientific evidence that PO4 "leaches" from live rock/dry rock? Meaning: purpose driven research geared around this exact topic.

Or is this just another "reef keeping egregore"?

 

[Garf]

So I have battled high phos for a long time. GFO does work, but I have this issue where when I get it down to a reasonable level (.1-.3), i stop GFO, and it just goes back up.

I just wonder when I might every see this stabilize.

I do not have algae issues on any rocks.

You are adding phosphate every time you feed the tank. It doesn't evaporate but can be bound to surfaces in the tank, especially calcium carbonate. Therefore, it naturally rebounds as the phosphate removal method is deleted or reduced. The phosphate is unbound from surfaces as the bulk water phosphate level reduces. However, I think this flow from rocks has absolutely nothing to do with algae infestations.

 

[Bear22]

You are adding phosphate every time you feed the tank. It doesn't evaporate but can be bound to surfaces in the tank, especially calcium carbonate. Therefore, it naturally rebounds as the phosphate removal method is deleted or reduced. The phosphate is unbound from surfaces as the bulk water phosphate level reduces. However, I think this flow from rocks has absolutely nothing to do with algae infestations.

I agree.

Planet-wide there is a PO4 cycle; soil, rock, water, and even the atmosphere transport/cycles a small amount of PO4.

I'm skeptical about the live rock/dry rock vector with respect to algae blooms/outbreaks.

 

[Garf]

I agree.

Planet-wide there is a PO4 cycle; soil, rock, water, and even the atmosphere transport/cycles a small amount of PO4.

I'm skeptical about the live rock/dry rock vector with respect to algae blooms/outbreaks.

Dry rocks can provide great attachment sites for algae due to the pore size / texture of the surface, and the lack of other organisms which either prevent attachment or predate on them. Cement has an ideal surface for GHA, for example. Even then, given enough time and herbivore activity, these too develope to less tasty or harder species.

 

[Garf]

5. The glass has not needed cleaning as much.

I have actually experienced this with a DIY scrubber, a long time ago. Not sure how you relate that to phosphate flow out of rocks, when the bulk water levels were relatively very high, tbh. I attributed it to an unknown release of inhibitory compounds by the algae on the screen.

 

[Bear22]

Dry rocks can provide great attachment sites for algae due to the pore size / texture of the surface, and the lack of other organisms which either prevent attachment or predate on them. Cement has an ideal surface for GHA, for example. Even then, given enough time and herbivore activity, these too develope to less tasty or harder species.

Honestly,

Just about any surface can present an affinity for algae to adhere to given the right circumstances.

Example: Even aquatic plants and their leaves can be major collection points for algae growth.

 

[mook1178]

Any solid scientific evidence that PO4 "leaches" from live rock/dry rock? Meaning: purpose driven research geared around this exact topic.

Or is this just another "reef keeping egregore"?

https://www.researchgate.net/public...hosphate_on_Calcite_and_Aragonite_in_Seawater

 

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So I have battled high phos for a long time. GFO does work, but I have this issue where when I get it down to a reasonable level (.1-.3), i stop GFO, and it just goes back up.

As you continue to pull P from the rocks, the P level in the water will stabilize at lower and lower levels when you stop GFO. That lowest level is a balance of feeding vs scrubbing.

Any solid scientific evidence that PO4 "leaches" from live rock/dry rock?

It's pretty well known in the literature, so I didn't include any. As for anecdotal, it's predictable and reproducible, and I've seen it hundreds of times.

I have actually experienced this with a DIY scrubber, a long time ago. Not sure how you relate that to phosphate flow out of rocks, when the bulk water levels were relatively very high, tbh.

The P might be high in the water, but it's the relative value compared to the rock, over time, that matters.

Even aquatic plants and their leaves can be major collection points for algae growth.

Yes a strong P filter will reduce P in the water enough that attached hair algae and even dust algae will be removed from plants, without harming or slowing the growth of the plants.

 

[Bear22]

As you continue to pull P from the rocks, the P level in the water will stabilize at lower and lower levels when you stop GFO. That lowest level is a balance of feeding vs scrubbing.



It's pretty well known in the literature, so I didn't include any. As for anecdotal, it's predictable and reproducible, and I've seen it hundreds of times.



The P might be high in the water, but it's the relative value compared to the rock, over time, that matters.



Yes a strong P filter will reduce P in the water enough that attached hair algae and even dust algae will be removed from plants, without harming or slowing the growth of the plants.

What is your definition of a "P filter"?