Bolus dosing

[Randy Holmes-Farley]

So, what really stops algal growth?

I think that’s a big question I’d like to know the answer to.

I think it varies, but in the case of many ATS systems, I think it might well be trace elements. :)

 

[Hans-Werner]

This is the part I do not get. Maybe understand is more proper. I feel that those of us with higher nutrient systems and no algae issues is because we have a balanced herbivore population. To me this includes fish, snails, hermits, and reef hardscape.

I see the growth on the glass panes but do not see anything on the reef structure. I clean the glass and my fish eat the algae. I see snail trails on the glass if I ignore it. I see astrea stars on the rocks along with mini stars and strombus snails. In my case high nutrients is 24 - 34 ppm nitrate and .70 to .80 ppm phosphate. I've kept my phosphate as high as 1.7 ppm.

Did you let the algae on the glass panes grow for several weeks? I sometimes do since the tanks are no display tanks. I can confirm that I see the snail trails of the Turbo and Trochus snails too. But do the glass panes ever grow hair algae or other nuissance algae? In our systems not. What comes after the green or brown microalgae with snail trails is more and more calcifying algae and coralline algae, especially in places that are hard to clean.

In my experience the needs of coralline algae are very similar to that of corals. Maybe they even have similar ecologic strategies (precipitating and monopolizing trace metals, low iron demand due to accessory pigments that don't require iron). Coralline algae and corals is a kind of climax stadium of reef tanks, little help of algivores needed.

 

[KStatefan]

In new tanks with artificial rock or sand, it is often observed that they initially bind a lot of phosphate. In many cases, PO₄ is dosed to prevent limitation—until a certain point when the bound phosphate is suddenly released, causing a sharp increase in PO₄ levels.

What causes the sudden release? Something has to change to cause that equilibrium point to change. I have never seen a cause given for this change.

 

[Garf]

What causes the sudden release

Suddenly realising you haven't tested for ages, or realising your test kit is rubbish, lol.

 

[areefer01]

Did you let the algae on the glass panes grow for several weeks? I sometimes do since the tanks are no display tanks. I can confirm that I see the snail trails of the Turbo and Trochus snails too. But do the glass panes ever grow hair algae or other nuissance algae? In our systems not. What comes after the green or brown microalgae with snail trails is more and more calcifying algae and coralline algae, especially in places that are hard to clean.

I clean the left side and front of the display about every three or four days. If I go any longer it impedes visibility. I would say that most of the film type algae management is done by my Strombus maculatus snails (on rocks). They leave the trails on the glass. They routinely lay eggs and the population seems to ebb and flow based on the availability of their food. I see them on the glass panes and on some of the rocks. I do not have any coralline algae visible on my glass. In fact I do not really have it on the rocks either interesting enough. That could be due to the urchins or high phosphates. I'm not sure to be honest.

With regards the glass pane and nuisance algae. This gets back to my opinion that visible signs of nuisance algae in our display is a improper herbivore selection and number. Below is an image of hair algae on one side of my display with a red scarlet hermit working through it. This is a still taken from a video I captured.

I should note I'm just sharing my experience. I do not bolus dose as it is counter-intuitive to me.

.

 

[Luminous74]

What causes the sudden release? Something has to change to cause that equilibrium point to change. I have never seen a cause given for this change.

I can’t say for sure what causes the sudden release—that’s something others here, who are more specialized in the topic, can probably explain better than I can. However, this phenomenon has also been described by many other reefkeepers who experienced a similar PO4 spike under comparable circumstances.

In any case, I’ve experienced it myself in my previous system—and no, it has nothing to do with a faulty PO4 test. I would even say that my PO4 measurements are very consistent and reproducible.

 

[Luminous74]

Suddenly realising you haven't tested for ages, or realising your test kit is rubbish, lol.

Now that you mention it – dang, I hadn’t thought of that!:eek::anxious-face-with-sweat:

 

[Luminous74]

In my 30-gallon tank, there's exactly one Trochus snail that eats algae – all the other inhabitants are not algae grazers.

When NO₃ is undetectable and PO₄ is below 0.03 mg/l, hair algae growth is strong. But once NO₃ rises above 1 mg/l and PO₄ is above 0.08 mg/l, the algae noticeably recede and almost disappear. The dosing of All-For-Reef has remained more or less constant during this time.

So I would assume that when nutrient levels are optimal for my corals and overall biology, trace elements for the algae become limited – and that’s what restricts their growth.

 

[Luminous74]

In my 30-gallon tank, there's exactly one Trochus snail that eats algae – all the other inhabitants are not algae grazers.

When NO₃ is undetectable and PO₄ is below 0.03 mg/l, hair algae growth is strong. But once NO₃ rises above 1 mg/l and PO₄ is above 0.08 mg/l, the algae noticeably recede and almost disappear. The dosing of All-For-Reef has remained more or less constant during this time.

So I would assume that when nutrient levels are optimal for my corals and overall biology, trace elements for the algae become limited – and that’s what restricts their growth.

 

[Pod_01]

Now that you mention it – dang, I hadn’t thought of that!:eek::anxious-face-with-sweat:

I suspect that is the case.

I only observed large shift in PO4 when I didn’t test for a long time.

 

[Luminous74]

I suspect that is the case.

I only observed large shift in PO4 when I didn’t test for a long time.

I would rule that out for my tank. I test PO₄ at least twice a week, and each time the increase happened quite rapidly. There were no changes to my feeding routine, and my freshly mixed seawater also showed undetectable PO₄ levels.

 

[Pod_01]

I would rule that out for my tank. I test PO₄ at least twice a week, and each time the increase happened quite rapidly. There were no changes to my feeding routine, and my freshly mixed seawater also showed undetectable PO₄ levels.

So just to step back, what exactly do you consider rapid increase? Just curious…

When I measured PO4 I used to measure long after any feeding or early in the morning before anything got into the water just to remove any possible contamination.

Rocks or sand can’t release PO4 like a sponge or desorbing it.
It either binds or unbinds when out of equilibrium with water. This is how all PO4 removal media like GFO works.

 

[Luminous74]

So just to step back, what exactly do you consider rapid increase? Just curious…

When I measured PO4 I used to measure long after any feeding or early in the morning before anything got into the water just to remove any possible contamination.

Rocks or sand can’t release PO4 like a sponge or desorbing it.
It either binds or unbinds when out of equilibrium with water. This is how all PO4 removal media like GFO works.

By a rapid increase, I mean a rise of about 0.1 mg/l within a week – without any significant changes on my part. The trend continues upward if no countermeasures are taken. However, I never felt it was an option to just let it keep rising.

Once the value reached 0.2 mg/l, I started taking action – for example, replacing the sand, which in my opinion is a very effective way to reduce elevated PO₄ levels.

I always measure early in the morning, before any feeding takes place. In cases of such significant deviations, I always perform a second measurement to confirm the result.

I also do ICP tests from time to time, and my measurements with the Hanna Low Range Phosphorus checker differ by no more than 0.03 mg/l from the ICP results. That’s why I have a high level of trust in my own measurements.

 

[Luminous74]

From my point of view, this is exactly the key issue: In the beginning, PO₄ binds to rocks or sand, keeping the level in the water low or even undetectable—until a saturation point is reached.

PO₄ is continuously introduced through feeding and, in some cases, through targeted dosing. At some point, the level in the water starts to rise, so you reduce or even stop dosing altogether—yet the PO₄ level continues to increase.

Why does that happen?

 

[Luminous74]

So just to step back, what exactly do you consider rapid increase? Just curious…

When I measured PO4 I used to measure long after any feeding or early in the morning before anything got into the water just to remove any possible contamination.

Rocks or sand can’t release PO4 like a sponge or desorbing it.
It either binds or unbinds when out of equilibrium with water. This is how all PO4 removal media like GFO works.

From my point of view, this is exactly the key issue: In the beginning, PO₄ binds to rocks or sand, keeping the level in the water low or even undetectable—until a saturation point is reached.

PO₄ is continuously introduced through feeding and, in some cases, through targeted dosing. At some point, the level in the water starts to rise, so you reduce or even stop dosing altogether—yet the PO₄ level continues to increase.

Why does that happen?

 

[Pod_01]

Why does that happen?

I been reefing for 6+ years and so far my reef tends to be PO4 happy…

By a rapid increase, I mean a rise of about 0.1 mg/l within a week – without any significant changes on my part.

I do not consider that a spike, just normal PO4 variation. My PO4 runs from 0.1-0.5 ppm and I don’t do anything. It trends up and it trends down, same feeding etc… As long as corals look happy I sit on my hands.

Perhaps your corals are missing some trace elements and due to the deficiency are not consuming the PO4 and the outcome leads to PO4 accumulation/ spike.

I feed my fish a lot, they are all nice and fat and I still dose Tropic Marin Phos Feed.

My suggestion, monitor PO4 but pay attention to the corals. If corals look happy do nothing.

Maybe don’t measure PO4 and just observe corals…
I check PO4 very seldom these days.

 

[Koty]

In my tank, a rise in phosphate is related to the skimmer getting clogged with critters and stuff. However with all export measures (and I use them all: Cheato, skimmer on 100% 27/7, heavy carbon dosing) I cannot get it below 0.2-0.1 mg/ml
This shows the effect of cleaning the skimmer. Each line is 0.1 mg/ml. Top is 0.9 (Probably over as is over the limit of the Hanna ULR)

 

[Koty]

In my tank, a rise in phosphate is related to the skimmer getting clogged with critters and stuff. However with all export measures (and I use them all) I cannot get it

 

[Hans-Werner]

I do not have any coralline algae visible on my glass.

Strange, I think I can see coralline algae in the image. What are the pink (and whitish grey bleached) patches on the glass?

I can’t say for sure what causes the sudden release—that’s something others here, who are more specialized in the topic, can probably explain better than I can. However, this phenomenon has also been described by many other reefkeepers who experienced a similar PO4 spike under comparable circumstances.

I don't think it usually is a release of phosphate. Did you calculate the phosphate supplied since your last testing? I think what really happens is this: You are dosing phosphate and it regularily "disappears" from the water because it is adsorbed by the phosphate-leached rocks and substrate. At some point rocks and substrate are saturated and the phosphate concentration suddenly jumps up. However, there is no adsorbed phosphate released, only the dosed phosphate remains in the water by near 100 %. This is what you see.

 

[areefer01]

Strange, I think I can see coralline algae in the image. What are the pink (and whitish grey bleached) patches on the glass?

There may be a spot but that is not what I was referring to. We have both seen surface area covered with it including glass panes with long running patches that scrapers and/or magnets have difficulty clearing. That is all I mean. I'll include a video from September 2024 below of my display. Again I was just replying about the herbivore part and how I believe a balance is vital to algae management. Not sure why I don't see it other than maybe the urchin is faster but it isn't on the glass. Not sure.

Here is a September 2024 short of my display.


Here is a short video in the same area the scarlet hermit was eating algae in. This was taken in 2022 and again in 2024 as I was documenting my pink square anthias growth and color.