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Old 10/22/2020, 10:44 PM   #1
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djryan2000's Avatar
Join Date: Aug 2019
Posts: 430
Dosing nutrients question

I use a Santa Monica drop 1.4x in my tank for nutrient control. I am putting less than 1.4 frozen cubes in daily as I donít have the fish to justify it (yet). Whatís happening is my phosphate bottomed our to 0 (confirmed by ULR Hannah checker) and nitrates creep up until I do a water change, leading to deteriorating coral health.

I am thinking that I should dose phosphate for now the time being, as I do have corals that are slowly starting to bleach out (especially my monti caps). Should I also get nitrates to dose on hand?

My understanding of algae is that it takes both nitrates and phosphates but once it runs out of phosphates growth stalls and it no longer pulls nitrates. Therefore, once I dose phosphates it will pull more nitrates out and I need to make sure I donít bottom them out at 0 as well.
Is this correct?

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Old 10/23/2020, 07:58 PM   #2
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Join Date: Jul 2010
Location: Austin, TX
Posts: 1,783
Phosphates come in a variety of flavors but the only one we can test for is PO4. Algae is competing with corals for nitrogen and phospahtes and there's some pretty complex biological warfare going on. Research ahs shown when corals become phosphate deficient they become very sensitive to light and temperature changes and even small increases in nitrates can cause issues. Southhampton University in England identifed a threshold level of .03 mg/l PO4. There's no magic number but since we can't test for all the types of phosphate to reduce the risk of hurting corals I suggest keeping PO4 roughly around .1 mg/l.

Here's some videos and links for more info:

Forest Rohwer "Coral Reefs in the Microbial Seas"

And "Changing Seas"

Richard Ross What's up with phosphate"

Links on PO4
An Experimental Mesocosm for Longterm Studies of Reef Corals

Phosphate Deficiency:
Nutrient enrichment can increase the susceptibility of reef corals to bleaching:

Ultrastructural Biomarkers in Symbiotic Algae Reflect the Availability of Dissolved Inorganic Nutrients and Particulate Food to the Reef Coral Holobiont:

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Effects of phosphate on growth and skeletal density in the scleractinian coral Acropora muricata: A controlled experimental approach

High phosphate uptake requirements of the scleractinian coral Stylophora pistillata

Links on algae, DOC and sponges

Indirect effects of algae on coral: algae‐mediated, microbe‐induced coral mortality
Coral seperated from algae with a .02 Ķm filter die. Treatment with aampicillan prevents death.

Influence of coral and algal exudates on microbially mediated reef metabolism.
Coral DOC improves oxygen (autotrophy), algae DOC reduces oxygen (heterotrophy).

Effects of Coral Reef Benthic Primary Producers on Dissolved Organic Carbon and Microbial Activity
Algae releases significantly more DOC into the water than coral.

Pathologies and mortality rates caused by organic carbon and nutrient stressors in three Caribbean coral species.
Starch and sugars (doc) caused coral death but not high nitrates, phosphates or ammonium.

Visualization of oxygen distribution patterns caused by coral and algae

Biological oxygen demand optode analysis of coral reef-associated microbial communities exposed to algal exudates
Exposure to exudates derived from turf algae stimulated higher oxygen drawdown by the coral-associated bacteria.

Microbial ecology: Algae feed a shift on coral reefs

Coral and macroalgal exudates vary in neutral sugar composition and differentially enrich reef bacterioplankton lineages.

Sugar enrichment provides evidence for a role of nitrogen fixation in coral bleaching

Elevated ammonium delays the impairment of the coral-dinoflagellate symbiosis during labile carbon pollution
(here's an argument for maintaining heavy fish loads if you're carbon dosing)

Excess labile carbon promotes the expression of virulence factors in coral reef bacterioplankton

Unseen players shape benthic competition on coral reefs.

Allelochemicals Produced by Brown Macroalgae of the Lobophora Genus Are Active against Coral Larvae and Associated Bacteria, Supporting Pathogenic Shifts to Vibrio Dominance.

Macroalgae decrease growth and alter microbial community structure of the reef-building coral, Porites astreoides.

Macroalgal extracts induce bacterial assemblage shifts and sublethal tissue stress in Caribbean corals.

Biophysical and physiological processes causing oxygen loss from coral reefs.

Global microbialization of coral reefs
DDAM Proven

Because sponges are essential players in the carbon, nitrogen and phosphorus cycle(s) on reefs here's some links to research done with them.

Element cycling on tropical coral reefs.
This is Jasper de Geoij's ground breaking research on reef sponges. (The introduction is in Dutch but the content is in English.)

Sponge symbionts and the marine P cycle

Phosphorus sequestration in the form of polyphosphate by microbial symbionts in marine sponges
(Chris Kenndall had a problem with low PO4 and had problems raising it with Neophos. Samples sent off showed phosphorus crystals developing in some of the sponges in his system accounting for at least some of his systems consumption.)

Differential recycling of coral and algal dissolved organic matter via the sponge loop.
Sponges treat DOC from algae differently than DOC from corals

Surviving in a Marine Desert The Sponge Loop Retains Resources Within Coral Reefs
Dissolved organic carbon and nitrogen are quickly processed by sponges and released back into the reef food web in hours as carbon and nitrogen rich detritus.

Natural Diet of Coral-Excavating Sponges Consists Mainly of Dissolved Organic Carbon (DOC)

The Role of Marine Sponges in Carbon and Nitrogen Cycles of COral Reefs and Nearshore Environments.

And since we're discussing favorable and not so favorable bacteria here's a paper looking at how different corals and polyps are influencing the bacteria in the water column.
Aura-biomes are present in the water layer above coral reef benthic macro-organisms

"Our crystal clear aquaria come nowhere close to the nutrient loads that swirl around natural reefs" Charles Delbeek
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