Is growing algae for nutrient export a bad idea?

[robert]

I think I will do a before and after experiment as I intend to get rid of my macros (cheato, dragon's breath) and just run UV. I will put up some pics and take some notes as well

Thats an interesting experiment...how long have you been running with macros? I think that the drag placed on your system is not initially aparrent - sort of like the boiling frog thing...but the results of sudden removal can be more evident.

In another thread https://www.reef2reef.com/threads/s...this-thing-sort-of.216694/page-6#post-2601080 @hatfielj also removed macros from his system and made this comment on what he saw:

"Its funny, I just changed my frag tank set up last week and I've noticed all of the sudden my acros/montis looking better and growing faster. I was previously running a refugium as part of my old frag tank. So now that its gone, I'm instantly seeing improvements. I can't say for sure this is the cause, but I'm not complaining. My corals are looking better than ever and actually growing faster..."
​

It would be interesting to see how it works out in your case.

 

[hatfielj]

Yeah, I'm still seeing way better colors and growth, polyp extension since getting rid of my refugium/macro algae set up. I think the algae was starving my corals of nutrients. The water was too clean. I have nitrate levels that are actually detectable now, which in the past never were. Its important to have some nitrates and phosphates in the water, but keep them in check. Another thing I noticed when I removed my refugium and added a new frag tank was that I had a brief diatom bloom. Corals can consume diatoms (check out Dana Riddles articles on coral nutrition in Advanced Aquarist). So I think my corals got a much needed meal during that phase.

 

[mcarroll]

I didn't notice this in the thread yet, @robert. Have you (or anyone else) seen this yet?
http://www.sciencedaily.com/releases/2006/06/060612221839.htm

"Our study shows that bacteria are the front line that kill corals," Smith explained. "Algae release sugar, fueling bacterial growth on the corals. These bacteria suffocate the coral by cutting off the supply of oxygen.

[...]scientists[...]put algae and coral in chambers of seawater with filters between them. All of the corals with neighboring algae died, while coral without neighboring algae did not die. However, with the addition of an antibiotic, coral death even in the presence of algae was prevented, showing that bacteria fed by the algae are the agents of coral death.

At the very least we seem to be getting quite solid evidence against carbon dosing with vodka or sugar. But, there's clearly at least something to your thread title as well!

 

[mcarroll]

I don't think we know what causes burnt tips, but one prevailing idea told to me be Charles Delbeek is that the high alk causes skeletal growth faster than low nutrients will allow good tissue growth. So the tissue at the growing tip gets very thin and susceptible to damage, such as by light.

As I understand it, burnt tips can come about from other ways of reducing nutrients, such as GFO, which do not have a bacterial or CO2 component.

Bear with me here...it's late and I'm out of reading and writing time for the night. Clarity may suffer. Also, even if interesting, this may be better in its own thread...sorry.

Carbon Craziness
The literature seems to have too much info on carbon related coral issues (my tie-in to the thread! LOL) for this to be the persistent mystery that it has become...known euphemistically as a "high alk problem" rather than a "carbon dosing problem".

From Coral Reefs: An Ecosystem In Transition, Section 4.5 (page 130)...
(I'm reading excerpts on Google Books from a $400 acedemic book, so I can't even copy/paste properly or even get access to a copy of the book....sorry in advance. Anyone with access to an acedemic library? See bottom for an attempt at screenshots.)

The Crux Of It
Carbonic anhydrase (CA) moderates the balance of CO2 and bicarbonate and is directly involved in coral skeleton formation.

CA in coral tissue is (one of) the crossroads between organic and inorganic carbon (DOC and DIC) sources in our tanks and the ocean.

My Take
My hypothesis is that carbon dosing is causing the problem of "burnt tips". Dosing bicarbonates for alkalinity is merely activating a symptom by eliciting "burnt tips". The coral is living in an impaired state, in my opinion. I think the research supports this.

By dosing a tank with additional bicarbonates (i.e. keeping dKH >8) when the carbonic anhydrase in the coral's tissues may be coping with other excess carbon sources could be one source/aspect of the burnt tips phenomena. Put another way, carbon dosing might inhibit or defeat a coral's ability to deal with (e.g.) acidosis during night cycles. GFO messes with alkalinity, pH and calcification (among other things which may also relate) - so I suspect it has a role in this explanation...and why "burnt tips" sometimes occurs with its use.

@Randy Holmes-Farley covers this angle on GFO somewhat in two sections of this article. A tiny quote:

..reported effects [of GFO usage] include tissue recession..

Consistent with "burt tip" symptoms, but that conclusion was not drawn...not back in 2004, anyway!)

Enough blathering (for now!)...hopefully my thoughts aren't completely obscured.

Screenshots
Don't know if this will be allowed, or even legible. (Someone holler if these need to be removed.)

I'm not sure what my commentary has added, so I'm gonna try some screenshots of the referenced section....would like some feedback. FYI, it's dense, and some material at the beginning will be familiar...please read on to the end. :

 

[Randy Holmes-Farley Verified Community Expert]

I'm not sure I understand the idea above.

Carbonic anhydrase only accelerates the equilibrium in the reaction below (both ways are speeded up)

H2CO3 <--> H2CO3

The reverse reaction is speeded up from taking seconds to taking much less than seconds.

So with that as what it does, how do you propose is it involved in a theory of burnt tips and organic carbon dosing?

FWIW, I do recognize it plays a role in calcification (which I discuss in the article below). I'm just not seeing a connection to burnt tips.

Aquarium Chemistry: The Chemical and Biochemical Mechanisms of Calcification ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/2002/4/chemistry

 

[CastAway]

Tagging along.

 

[WetWhistle]

My tank consumes cheato unless I dose nitrate lol

My buddys tank did the same thing till he took out the baffles out of his sump. He was constantly at 0 for nitrates and phosphates and had to dose all the time. He took them out and now they hover at just enough he doesn't have to dose and his sps colors are great.

 

[WetWhistle]

All I run in my sump is Caulerpa and a few mangroves for my nutrient processing with some carbon in a bag and a skimmer. I have no issue with nuisance algae growth in my tanks as the macroalgae and mangroves out compete other algae for the limited available resources. Not only does the macroalgae use up nutrients it helps foster the food web and in turn this eats any algae that might grow. I have been a strong believer of using macro algae for filtration long before it was popular and I have never had an issue with it. Just my 2 cents.

 

[mcarroll]

• CA seems to be inherent to their control of calcification...though "not well understood."
• "Night acidosis" seems to be one of the things corals "manage" with their control of CA.
• "Burt tips" (and maybe some other forms of tissue loss) seems to be a loss of this control.
• A "specialized" CA was found to reside (or be expressed) exclusively in coral septa of "adults."
• There seems to be evidence that messing with their "carbon evironment" can be deleterious. Some amino acids and amines may also figure in.
• Depending on the source of carbon, this extracellular CA can convert to DIC (seems a benefit) or be used to remove CA from the location.
• Hydrogen removal in this process uses another enzyme, which is another pathway we might be inadvertantly tweaking.
• CA is also involved in carbon-concentration for the zoox, not only in calcification. Poorly understood, but another pathway we may be unknowingly tweaking.
• From Section 5..light, pH and "carbon chemistry" all play a role in calcification.
• Photosyntheis is required to facilitate removal of hydrogen ions.
• Calcification increases when carbonates are dosed, but photosynthesis is not increased. This seems to set up conditions for H+ buildup.
• The link that @robert posted showed tissue loss and mortality clearly with various sugars (but not from nutrients).

Gonna have to circle back to this - out of time again. (And still no time for editing...tell me if that's making any sense.) If you haven't at least read through that part of Section 4 and at least the beginning of Section 5 that I just mentioned, please do so.

 

[beaslbob]

actually Macro and other algaes serve two functions.
first nutrient export
second nutrient recycling.

algae recycles nutrients into fish and coral food in the form of the algae itself plus pods and bugs as well.

IMHO as long as the corals get first crack at the nutrients all the macros do is get the nutrients missed by the corals.

my .02

 

[Randy Holmes-Farley Verified Community Expert]

Sorry, I don't seem to be able to connect the dots between organic carbon dosing, carbonic anhydrase, and burnt tips.

I don't understand the basis of the conclusion in your third sentence:

• CA seems to be inherent to their control of calcification...though "not well understood."
• "Night acidosis" seems to be one of the things corals "manage" with their control of CA.
• "Burt tips" (and maybe some other forms of tissue loss) seems to be a loss of this control."

You are thinking that burnt tips relates to internal pH issues? Why?

I also cannot tell what this one means, since I'm not sure how organic carbon has any relationship to carbonic anhdyrase except in how organic carbon may increase CO2 levels when it is broken down by other enzymes.

• Depending on the source of carbon, this extracellular CA can convert to DIC (seems a benefit) or be used to remove CA from the location."

 

[mcarroll]

Ya, will take some more time for me to digest and explain any better.

Wish I had experience in digesting and explaining this kind of writing - I'm sure it would go faster.

More to come...

 

[NanaReefer]

This is hurting my brain [emoji12][emoji13]

 

[beaslbob]

This is hurting my brain [emoji12][emoji13]

u 2 hu???????

 

[mcarroll]

@robert & fellow thread followers...another link of interest (don't think it's a duplicate):

Effects of Coral Reef Benthic Primary Producers on Dissolved Organic Carbon and Microbial Activity

 

[robert]

@mcarroll - thanks for the link - right on point.

 

[wpeterson]

Thanks for an interesting discussion on this topic so far. Macro-algae in refugia seem to have a widely accepted track record for nutrient export.

There also seems to be evidence for macroalgae releasing sugars and other carbohydrates into the water column and increasing the DOC levels. There is linkages to higher DOC levels increasing risk of bacterial infection/overgrowth in corals and other negative effects. It seems reasonable to link a larger macro-algae refugium to negative impacts on corals through this channel.

However, the increased DOC could largely be removed or counter-acted through use of carbon reactors and other carbon export mechanisms - so people may see dramatically different results on the coral in their tank due to the secondary impact of carbon export (via reactors) or import (via dosing).

I would love to see three separate systems with coral and chaetomorpha in identical setups, but one having aggressive activated carbon filtration, one having no filtration, and one having no filtration and carbon dosing.

Some day I'll have a home with more space where I could run an experiment like this for 6 months, I think it would be fascinating. It would also be easier to gather compelling evidence if DOC were easier to measure without expensive lab equipment.

 

[mcarroll]

Thanks for an interesting discussion on this topic so far. Macro-algae in refugia seem to have a widely accepted track record for nutrient export.

There also seems to be evidence for macroalgae releasing sugars and other carbohydrates into the water column and increasing the DOC levels. There is linkages to higher DOC levels increasing risk of bacterial infection/overgrowth in corals and other negative effects. It seems reasonable to link a larger macro-algae refugium to negative impacts on corals through this channel.

I agree, very interesting.

The linkage you mention is the microbial community...or the microbial food web.

MFW

(Link #3 on my favorite chem links thread.)

We use modulation of that food web - or attempt to - all the time - usually to compensate for high livestock rates. Or "filtration".

"Carbon dosing" and use of algae and macroalge to compensate for high livestock rates are two common "tools" that folks use.

The interesting thing is that I doubt many of us that carbon dose or employ large masses of algae are thinking beyond "filtration". There's definitely more to the story!