Hair Algae, A Case Study.

[victoly]

So it's pretty much just nutrient export via WC and then adding in bio to do the heavy lifting?

[mFrame]

So it's pretty much just nutrient export via WC and then adding in bio to do the heavy lifting?

Yep, nutrient export via water change and physical removal. I have seen a boom in Anthelia growth (the next pest to go) and in micro-feather dusters. I believe they're picking up some of the slack of nutrient export as the algae diminishes.

Tim prodded me to mention that I had become very lax on changing my GFO and activated carbon (been, oh, 9 months or so). Additionally I had an undetermined period of time where my sump bulb had burned out and I hadn't noticed, so I lost most of the chaeto and other macros that were also doing nutrient export.

[Timfish]

Here's the water parameters and a picture from Friday:

Alkalinity 13

pH 8.2

Calcium 480

Nitrate trace

PO4 3-4 mg/l

Magnesium 1680

So it's pretty much just nutrient export via WC and then adding in bio to do the heavy lifting?

Water changes haven't done much nutrient removal. Water changes I think are a little smaller than Mike said more like 20% - 25% (35 - 45 gallons on a 200 gallon system). Nitrate has been constant at 5 mg/l until sometime in the last six weeks when it dropped to just a trace. Phosphate levels have stayed pretty much the same around 3-4 mg/l. The first few water changes saw a lot of nuisance animals and algae removed but that was exporting nutrients that had already been fixed and taken out of the water column. The algae that was removed with the water changes June through September has been pretty minimal, just 20-30 minutes of touch up work with a tooth brush or tube brush on stuff where the urchins can't get to. None was done in October or this last week.

And I wouldn't say the "bio" we added removed much either. A couple additional urchins were added at the beginning but several were already in the system. I'm sure they've grown some which would fix some nitrate and phosphate but a lot of the nutrients fixed in the algae they scour off the rock is put back in the system and is available for both the algae and corals.

This scenario is something I've seen repeatedly and what best explains it is not a problem with "nutirents" but with DOC, (Dissolved Organic Carbon). What is commonly promoted is "excess nutrients => nuisance algae => coral problems" or "excess nutrients => coral problems => nuisance algae" and the solution given is to aggressively remove phosphate and nitrates often with skimming which does a poor job of removing DOC. There are certainly times when that might be the situation but since corals are competing for the same nutrients the algae want, even bypassing the nitrogen cycle in the tank by directly removing ammonium and uric acid from the water column, very different scenarios occur which let algae take over. Looking at the research done by and compiled by Forest Rohwer and presented in his book "Coral Reefs in the Microbial Seas" DOC is the real culprit in many situations, not phosphates or nitrates. Since corals can thrive in "high nutient" systems with little or no nuisance algae the sequence "Stressed coral => nuisance algae => excess DOC => coral problems => nusance algae . . ." is a much better explaination. This feedback loop that benefits nuisance algae at the cost of corals Rohwer goes into more detail with his DAMM model of reef degredation. In our aquariums by physically removing the source of the DOC causing problems with the corals lets the corals recover and start competing. in Mike's tank as the corals started to recover the algae started to slow down and it was the corals not the water changes that finally reduced the nitrates AFTER the nuisance algae problem was taken care of (unless you're going to argue a roughly 20% water change removed roughly 80% - 90% of the nitrates).

What can be the initial trigger that causes the corals to have problems can be a range of things. In Mike's case it was changes in his schedule that kept him from doing periodic maintenace. In my experience one of the biggest culprits is using GFO indesrciminatley which prevents corals from using nitrates which give nuisance algae an edge on the corals to grow and then we get in to the DOC feedback loop Rohwer describes. Temperature swings, especially above 84 or 85 degrees, can cause stress to the corals and temporarily stop them from feeding and growing, again giving algae a window of opportunity (even though corals may look fine, stress from heat shock can take weeks for them to recover and pathogenic microbes populations in their holobiont to return to normal levels). Stress from moving, it takes corals a long time to acclimate sometimes. Having new corals die definitely benefits the nuisance algae over established corals (I am always very slow to add new animals and make sure I know their lighting requirements and the history of the system they grew in if at all possible).

[victoly]

You know who has a total carbon analyzer in his lab? This guy... I've read the Feldman paper, and i think I understand the concepts pretty well.

Excess nitrogen/phosphorus => proliferation of DOC producers (i.e., ugly cyano/algae) => excess DOC => Excess nitrogen/phosphorus vis a vis nuking DOC-sensitive species

Is the argument then that nitrogen/phosphorus are not limiting to cyano/algae ? Because as autotrophs, algae/cyano should be producing DOC and not consuming it.

I like the theory, I'm just don't have a good grasp on the fluxes (how much DOC the coral holobiont is happy with vs. how much has a negative influence).

Maybe the answer is biopellets then. You locally increase DOC and skim them out, of course hopefully that doesn't result in a release of DOC to the tank...

[Timfish]

And maybe it's time for an update. The last year and half have seen sporadic 15% water changes between 3-4 weeks to 3-4 months apart. There's been no return of the hair algae and even in the holes and crevices that the urchins can't get to pretty much all of the hair algae has disappeared. Here's a couple recent pictures. (The bleached frogspawn Mike got in that condition to hopefully recolor back up.)

[Timfish]

You know who has a total carbon analyzer in his lab? This guy... I've read the Feldman paper, and i think I understand the concepts pretty well.

I gotta say the first question that comes to mind since we've discussed this several years ago when you still had a reef system is what were the TOC levels in your system? Feldman's research is very important to understand as it's the first research that looks at TOC in aquaria and how skimmers affect it and bacterial counts but it doesn't look at the effects of DOC produced like Rohwer covers in his book "Coral Reefs in the Microbial Seas" For those intersted in reading the papers by Feldman, et al, here's the links:

Bacterial Counts in Reef Aquarium Water

http://www.advancedaquarist.com/2011/3/aafeature

Granular Activated Carbon Pt 1

http://www.advancedaquarist.com/2008/1/aafeature1

Granular Activated Carbon Pt 2

http://www.advancedaquarist.com/2008/2/aafeature1

Total Organic Carbon Pt 1

http://www.advancedaquarist.com/2008/8/aafeature3

Total Organic Carbon Pt 2

http://www.advancedaquarist.com/2008/9/aafeature2

Protein Skimmer Performance, Pt 1

http://www.advancedaquarist.com/2009/1/aafeature2

Protein Skimmer Performance, Pt 2

http://www.advancedaquarist.com/2010/1/aafeature

Skimmate Analysis

http://www.advancedaquarist.com/2010/2/aafeature

. . . Excess nitrogen/phosphorus => proliferation of DOC producers (i.e., ugly cyano/algae) => excess DOC => Excess nitrogen/phosphorus vis a vis nuking DOC-sensitive species . . .

With the exception that corals are also producing lots of DOC this model is a decent summation of what happens to reefs impacted by agricultural runoff and/or sewage but it doesn't fit what happens when reefs loose the primary algae controls. In the Pacific overfishing impacts the reefs by removing as much as 80% of the fish biomass. (That's a lot of fish poop and piss the corals are missing.) This overfishing includes the large parrotfish that are responsible for keeping nuisance algae under control and clearing off places for larval coral to settle. In the Caribean it's the dieoff of Diadem urchins in '83 from a bacterial pathogen that's primarily responsible for proliferation of algae and the loss of clean rock for coral larva to settle and deterioration of the reefs. I think Mike's tank is an excellent example how it's not nitrate and phosphate per se that causes algae problems.

. . . Excess nitrogen/phosphorus => proliferation of DOC producers (i.e., ugly cyano/algae) => excess DOC => Excess nitrogen/phosphorus vis a vis nuking DOC-sensitive species . . . Because as autotrophs, algae/cyano should be producing DOC and not consuming it.

I like the theory, I'm just don't have a good grasp on the fluxes (how much DOC the coral holobiont is happy with vs. how much has a negative influence).

Maybe the answer is biopellets then. You locally increase DOC and skim them out, of course hopefully that doesn't result in a release of DOC to the tank...

Both corals and algae are producing DOC. The difference is the DOC produced by algae promotes heterotrphic (oxygen depleting) microbial populations, some of which are pathogenic to corals. The DOC produced by corals promote autotrophic (oxygen enriching) microbial populations. (By definition algae and cyano are autotrophs but looking at thier effect I think it makes sense to treat them as functional heterotrophs and corals as functional autotrophs in our systems.) As far as carbon dosing one of the studies Rohwer used for his DDAM model (he devoted a whole chapter to it in his book) looked at the effect of PO4 and nitrate enrichment and carbon dosing on corals it was the carbon dosing used that caused coral death not the increase in phosphate and nitrates. Rohwer's book is an excellent introduction to the research on DOC on reefs.