Low Nutrients, Pale SPS, Algae?

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Qantos

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Hi All,

My phosphate and nitrate is undetectable and my SPS are quite pale. Surprisingly, I've been noticing more algae on the sand bed and glass recently. Not hair algae, but just a green discoloration on the sand and typical green film on the glass.

I'm pretty perplexed by this. My fish population is low and I have a large skimmer and plenty of live rock in the sump. I feed only PE mysis and not a lot of it. I believe my nutrients are very low and this is why my corals look so pale.

If this is true, why the algae problem? Can some strains of algae thrive in a low nutrient system? I want to start feeding more to get my nutrients up and improve the color in my coral but I don't want to exacerbate the algae issue.

Thoughts?
 

Azedenkae

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If this is true, why the algae problem? Can some strains of algae thrive in a low nutrient system? I want to start feeding more to get my nutrients up and improve the color in my coral but I don't want to exacerbate the algae issue.
Well, yes in a sense. I would not say that they 'thrive' in a low nutrient system, in that they are very good at outcompeting anything else for nutrients, and so will be the first to be able to uptake it and grow. Leaving other organisms like coral starved. In a higher nutrient system, both types of organisms will be able to consume nutrients, but algae still better. So not so much that algae thrive under low nutrient conditions, they just survive it better than other organisms.

With that said, I would suggest feeding more and let the algae grow if they want. I find that systems where algae are actually scarce while corals are thriving is where there are already so much coral and so little algae that the corals actually outcompete the algae for the same nutrients, but those tend to be very well established aquariums. I would not sacrifice the health of corals just to keep algae in check. I'd feed as much as sensible, and remove algae manually if/when it starts bothering corals and/or looks ugly enough.
 
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Qantos

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Well, yes in a sense. I would not say that they 'thrive' in a low nutrient system, in that they are very good at outcompeting anything else for nutrients, and so will be the first to be able to uptake it and grow. Leaving other organisms like coral starved. In a higher nutrient system, both types of organisms will be able to consume nutrients, but algae still better. So not so much that algae thrive under low nutrient conditions, they just survive it better than other organisms.

With that said, I would suggest feeding more and let the algae grow if they want. I find that systems where algae are actually scarce while corals are thriving is where there are already so much coral and so little algae that the corals actually outcompete the algae for the same nutrients, but those tend to be very well established aquariums. I would not sacrifice the health of corals just to keep algae in check. I'd feed as much as sensible, and remove algae manually if/when it starts bothering corals and/or looks ugly enough.
Great response. This makes a lot of sense and pretty much confirms my suspicions. Thanks Azedenkae!
 

shred5

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Corals can be pale because for allot of reasons.
It may not be low nutrients. Algae increases goes against that but It may appear you have low nutrients because the algae is consuming the nutrients.
 

Dkmoo

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Also keep in mind nutrient is not only "no3 and po4". From a corals perspective, "nutrient" means meaty pieces of food and dissolved organic that the polyps will grab on directly, plus organic compounds and amino acids that they absorb thru their skin. "No3/po4" for the most part is absorbed in the zoox inside the coral. When you feed the tank, nutrient naturally break down from the solid food, to disolved organic compounds, to no3/po4. Thats why when you feed more, you increase the abundance of nutrient in all these levels and corals keep happy. Measuring and chasing only no3/po4 numbers will not give you a complete picture of what corals may be missing. This is also why directly dosing no3/po4 sometimes backfire depending on which level of the nutrient is deficient for corals in your specific tank

Algae absorbs no3/po4 only.
 
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