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View Full Version : Mineral depletion by algal scrubbers.



Broder
10-19-2009, 04:55 AM
I've been running a skimmerless mixed reef aquarium for a year now. Prior to that it's been running for 2 years with a skimmer. I religiously do 15% water changes with NSW on a weekly basis. In the last 3 months I started having problems with my SPS corals, resulting in the loss of a millepora colony and an acropora granulosa colony. Last week my prized staghorn, which I grew from a frag, started showing signs of stress, ie. no polyp extension. On friday STN started on the tips and at the base, typical iodine depletion symptoms. The same symptoms as the other 2 losses. I've done a 15% waterchange followed by a 25% waterchange this weekend, and dosed the tank with iodine solution. This seems to have slowed the necrosis down.

http://i216.photobucket.com/albums/cc82/Brodersfish/P1060049.jpg
This is the coral that is dying.

I'm not confident about this coral recovering, but I would just like to point out to scrubber users out there that this form of filtration comes with hazards. Very few of us measure our total iodine consumption and dose accordingly. What about other minerals that the algae is consuming along with nitates and phosphates? Iron, potassium, magnesium are consumed as well. Are there others? Even with my waterchange regime, some or all of the trace elements have been depleted to dangerous levels. I'm expecting an iodine test kit this week and will post current levels, although they will not reflect the level that caused the onset of STN/RTN in my corals.

I'll test as many of the trace elements as I can. Mg is at 1375ppm, so that's ok. Others will have to wait untill I can find test kits. I've been useing a scrubber for a year now, and am by no means a scrubber basher, but please be aware that there may be serious shortcomings to this system.

schnitm
10-19-2009, 08:10 AM
Can you give us some details?

Take size and population? What and how much do you feed? Where does your NSW come from? How big is your scrubber and how much to you harvest?

As I understand it, our little micro reefs are capable of consuming much more iodine than we can supply with water changes alone. Feeding is often the largest iodine input.

SantaMonica
10-19-2009, 08:19 AM
Sorry to hear of the troubles.

If it were the scrubber, then these problems would have occured long before they did, and, they would be occuring in everyone else's tanks too... not just those who run scrubbers (1000's just on my threads), but also everyone who uses macros in the fuge. Fortunately (although certainly unfortunate for your situation) yours is the only reported case like this.

My understanding is that the food you feed contains far more iron, iodine, etc etc than what algae and corals use. I myself have been experimenting with adding iron and iodine, and have seen no difference between adding tons of it, and none.

Broder
10-19-2009, 11:44 PM
Can you give us some details?

Take size and population? What and how much do you feed? Where does your NSW come from? How big is your scrubber and how much to you harvest?
The water parameters are near to that of NSW wrt kh, ca, sal, etc. I harvest a dry mass of 29g a week, but that's irrelevant. What is relevant is that the system is exporting all of the nutirents that need to be exported. ie. NO3=0 PO4=0.

As I understand it, our little micro reefs are capable of consuming much more iodine than we can supply with water changes alone. Feeding is often the largest iodine input. So you are saying that they balance each other out?

Broder
10-20-2009, 12:27 AM
Sorry to hear of the troubles.
Thanks, but after water changes and iodine dosing, the necrosis seems to have slowed down considerably. Lets just say, I'm not asking "who's next" but rather looking at being able to save this coral.

If it were the scrubber, then these problems would have occured long before they did, and, they would be occuring in everyone else's tanks too... not just those who run scrubbers (1000's just on my threads), but also everyone who uses macros in the fuge. Fortunately (although certainly unfortunate for your situation) yours is the only reported case like this.
I beg to differ on all of those statements. There are not that many sps/mixed reefs that have been running for a full year with a scrubber, especially a powerful one like mine. On the site where I am active there are at least 2 reported case of sps loss after scrubbers were introduced. Iodine depletion was suspected in both cases, dosed and resolved. Please see depletion of minerals and accumulation of toxins as a cumulative process. Mine has taken a year to surface, quite possibly because of the buffering effect of my strong waterchange routine. Fair enough, people have been harvesting macros from fuges for years, but we all know that they remove far less biomass from the system than a scrubber would.

My understanding is that the food you feed contains far more iron, iodine, etc etc than what algae and corals use. I myself have been experimenting with adding iron and iodine, and have seen no difference between adding tons of it, and none.
I'll dismiss this as anecdotal evidence in the absense of measurements. It would vary from tank to tank anyway. Are you measuring iodine and iron levels before and after dosing? You won't see a difference in your corals for as long as the levels are within parameters of what the coral needs. It's a fraction over or under that's going to cause the excrement to hit the ventilation.

This is a call to reefkeepers to be aware that there are pittfalls to any system of nutrient export. Be aware of them, watch out for them by testing levels of toxins as a scrubber will remove some of them, but many are locked in the substate/DSB and liverock. It is important to realise that inbalances are cumulative and it could take a year or more before a mineral has been depleted to dangerous levels.

Most importantly post the results of any testing and depletion that you may have encountered so that we can be aware of shortcomings and guard against them.

ChrisD
10-20-2009, 02:58 AM
A very interesting and, it seems, considered view. Thankyou for the warning. I have just got my scrubber up and running last night. Haven't done an iodine test in a while (always used to look at my xenia as an indicator) but I have a kit and will do a test tonight and monitor going forward.

Is it posible that you got some contaminated NSW and then your subsequent changes have diluted the contaminant to a point where the coral started improving? Just another possibility I can think of. Also out of interest, when you say your ATS is powerful, what are the specs vs tank etc. From what I have read, phosphates tend to be the limiting factor in the growth so does it not make it a self-limiting process. If you put a 20" ATS on a nano is it not simply a case of you will not get much growth on the screen?

The eradication of hair algae and valonia from my DT is high on my list for this scrubber but I'd hate for any corals to go too!

Sorry to hear of your losses, I hope the staghorn pulls through.

edit: Has the export form the scrubber been consistent in the lead up to your troubles? Just wondering if a sudden increase in export could have out paced the replacement from water changes.

Broder
10-20-2009, 05:37 AM
A very interesting and, it seems, considered view. Thankyou for the warning. I have just got my scrubber up and running last night. Haven't done an iodine test in a while (always used to look at my xenia as an indicator) but I have a kit and will do a test tonight and monitor going forward.
As you know the iodine kits have a short life-span, so just check that. That's the gist of what I'm saying..... That we must monitor as many parameters as we can. Be pro-active.

Is it posible that you got some contaminated NSW and then your subsequent changes have diluted the contaminant to a point where the coral started improving? Just another possibility I can think of.
Anything is possible. I've learnt that in reefkeeping there are no absolutes and it's guesswork most of the time.

Also out of interest, when you say your ATS is powerful, what are the specs vs tank etc. From what I have read, phosphates tend to be the limiting factor in the growth so does it not make it a self-limiting process. If you put a 20" ATS on a nano is it not simply a case of you will not get much growth on the screen?
There are 2 screens of 50cm x 30cm each serving a 600 liter system
http://i216.photobucket.com/albums/cc82/Brodersfish/Scrubber%20Photos/P1010574-1.jpg

http://i216.photobucket.com/albums/cc82/Brodersfish/Scrubber%20Photos/P1010572.jpg

http://i216.photobucket.com/albums/cc82/Brodersfish/P1060062.jpg


The eradication of hair algae and valonia from my DT is high on my list for this scrubber but I'd hate for any corals to go too!

Sorry to hear of your losses, I hope the staghorn pulls through.

edit: Has the export form the scrubber been consistent in the lead up to your troubles? Just wondering if a sudden increase in export could have out paced the replacement from water changes.
Absolutely consistant for the last 10 months but I'm sure that you are right that there has been a progressive decrease in some minerals.

schnitm
10-20-2009, 06:14 AM
I want to clarify my questions. I believe it is quite possible for an ATS to strip trace elements too low for some residents of a reef tank. I think Broder may be pointing at one situation where this can happen. I also think there may be a solution in Broder's experience. That's why I asked the questions.

I want to discuss three articles by Ronald Shimek. He compared the content of the water in 23 reef tanks and a sample of IO to NSW ranges. Then he tried to figure out why his samples we so remarkably different than NSW. Iodine was one part of his examination. I doubt there was an ATS in the group but let's look at this anyway:

1. http://www.reefkeeping.com/issues/2002- ... /index.php (http://www.reefkeeping.com/issues/2002-02/rs/feature/index.php) Here he shows us that the typical iodine levels (iodide actually) of reef tanks are much higher than NSW. Higher than IO too (and most (all?) salt mixes). Interestingly though, if you dig into this paper and the discussion of his work, 6/23 of the samples had no detectable iodide. They were below detection limits. So, most are higher, but there is a WIDE range.

2. http://www.reefkeeping.com/issues/2002- ... /index.php (http://www.reefkeeping.com/issues/2002-03/rs/feature/index.php) Here he did a correlation analysis. Take a look at Table 5. Iodine levels are positively correlated with nitrates, nitrites, and ammonia. Also there is a negative correlation between iodine and calcium additions. One interpretation...the more you feed, the more nitrates you have, the more iodine you have. Maybe as well, those with significant stony coral growth have tanks that use more iodine or they put less in.

3. http://www.reefkeeping.com/issues/2002- ... /index.php (http://www.reefkeeping.com/issues/2002-04/rs/feature/index.php) Here it gets really interesting. Typical reef tank feeding puts about 25% of the NSW content of iodine into the tank EVERY DAY! Those of us that feed relatively more (less) are put in more (less) iodine. Also, it seems ot matter what you feed. Algae does tend to concentrate iodine. Those of us feeding herbevores likely put more iodine into our tanks.

So back to Broder's situation. I am interested in how much you feed. Did you feed more after switching to the ATS? Do you have herbevores and what do you feed them. How high is your fish load? NSW seems to have considerable less iodine than salt mixes, which may be contributing.


And a question for everyone: Does an ATS tank need to be a well fed tank?

routestomarket
10-20-2009, 06:15 AM
MyFishEatYourFish on the MFK site: "update on my tank. no waterchanges since completion of ats over six months ago with multiple thriving sps, polyps, and a softies. [DT] algae growth is slowed, though what algae does grow is much harder than normal because it is corraline and that crappy tough brown stuff. my plants, chaeto and small grape calerpa show almost no growth, unfortunately xenia grows much slower than i would like too. one thing that everyone skimping on waterchanges must know is to keep up on additives, coral vite, calcium, magnesium, stonium, molebdenum essential elements etc. the best part is my nitrates and phosphates are still undetectable!!! thanks santa monica for starting this great thread!

It would seem that some people are aware of the problems you have described although you do state you do do regular water changes.

I am unsure of what the properties NSW (natural salt water?) is in Africa, but I do know if we tried that approach in the north of england we would probably end up with a turd in the tank! ;)

As you are going through the motions of checking the mineral levels in your tank water it may be pertinent to check your source water also, I remeber many years ago reading that if you are using natural water it needs to be collected some miles away from the shore to avoid runoff and contaminents from land drainage.

Like I say though this could well be different in your country!

Broder
10-20-2009, 10:06 AM
I am interested in how much you feed.
I feed heavily, although not more than is cosumed by the fish and corals, flake food, nori, peas, bloodworm, brine shrimp and marine mix.

Do you have herbevores and what do you feed them.
about 66% of the fish mass is herbivorous.

How high is your fish load?
I would consider it to be a mediumly stocked tank.

And a question for everyone: Does an ATS tank need to be a well fed tank?
I feel that is the beauty of a scrubber, if your tank is heavily fed the algae will grow more. If not, then it'll grow less. As for mineral depletion through less feeding, as you said, there is a wide spectrum of levels in the tanks tested in the study by Ron Shimek.

I don't want to focus too much on iodine levels in the algae scrubbed tank as I never measured the levels prior to my staghorn deterioration. For me the important thing is to realise that the scrubber is depleting minerals that need to be replaced.


As you are going through the motions of checking the mineral levels in your tank water it may be pertinent to check your source water also, I remeber many years ago reading that if you are using natural water it needs to be collected some miles away from the shore to avoid runoff and contaminents from land drainage.

Collecting water off-shore would be ideal. The problem with all forms of testing is that we're limited by the tests that are available to us. But you've given me an idea. One of our local beaches has recently acquired blue flag status, so water tests must have been performed. I'll try to establish the results.

routestomarket
10-20-2009, 10:17 AM
Collecting water off-shore would be ideal. The problem with all forms of testing is that we're limited by the tests that are available to us. But you've given me an idea. One of our local beaches has recently acquired blue flag status, so water tests must have been performed. I'll try to establish the results.

I think that should be your starting point! As outlined in the articles posted earlier it may be a change in the source water, you never know, it may be changes in the local ecology which have allowed the beach to gain blue flag status!

Our tanks are constantly in flux and as such it may be difficult to pinpoint the problem but I for one hope you do as your tank is stunning and any further losses need to be avoided!

SantaMonica
10-20-2009, 11:20 AM
One of the reasons I post on several sites is to get feedback from many users and situations (from actual users of scrubbers, not readers). That way, the differences will cancel out, and common items will appear. And indeed, many many common things have shown up, including problems that have been fixed with the current recommended setup. I'm currently posting on 30 sites (not including the "closed" sites like MASA), with over 1000 current scrubbers running on those sites. Several hundred of those were built when you built yours (there was an initial group back then who all tried it at the same time).

There are also the people who tried the old-style scrubbers (for about 15 years, up until June 2008). RC had a few hundred of these (because it's an older site), and there are more scattered elsewhere, many of whom where motivated by visiting Inland Aquatics. All these folks had not figured out the colored and cloudy water problem yet, but they did have strong filting (zero nutrients). These folks were also the more advanced aquarists, who at the time wanted to finally try a surge, because the units available then were the "real" dump version ATS ones per Aday's design.

Lastly, there are the studies/opinions (per above post) from Eric, Ron, etc., who have run scrubbers and who are in contact with many other scrubber users. BTW Eric and Ron have forums on MD if you want to inquire. Or you could maybe contact Inland too.

In all, up until your post, I don't recall reading a single report of coral trouble that came from the scrubber. One would think that if there were a situation where the problem could occur, even for a "strong" scrubber like yours, it would have occured at least in bits and pieces along the way. (BTW, yours is about the same as mine... about one watt per gallon, which many people have chosen to operate theirs at too. Some go much stronger.)

Hopefully this is good news. From a numbers point of view, I really think it would have surfaced before now.

schnitm
10-20-2009, 11:54 AM
I'm guessing not iodine then?

I do have to think a skimmer based system is going to favor some inhabitants differently than an ATS based system. Not to pick at the ATS concept, but shouldn't we expect a different equilibrium?

There's so little hard science. If this were one of my kidney patients at least I'd have 1000 publications (sponsored by pharmaceuticle compaines) to back me up. Then I can tell them in complete confidence that it's best to take their phosphate binder like the FDA says they should even though it tastes like chewing on a chalk stick. :roll:

routestomarket
10-22-2009, 04:14 PM
Broder,

I have a theory here but it does need some additional data to put in to practice or indeed share.

You mention a weight of yield per week, forgive me if this has been posted, but can you give me the weight both dry and freshly yielded.

Additionally, if you are feeding regular foods ie frozen / flake could you please approximate weights of both.

I appreciate you mention you have a large bio load which is fed heavily, could you please eleborate, how many fish, what size or overall size in inches of fish?

Finally and again apologies if posted already, overall capacity of enclosed system, Tank + Sumps + Cannisters or anything else.

I know I said finally, however, and I mean it this time, what filtration regimen do you have in place? Is this system maintained only by the ATS? :P

Many thanks in advance! You may either get an informed response or an apology that I missed something crucial but I think I have a thread here!

Broder
10-22-2009, 11:29 PM
but can you give me the weight both dry and freshly yielded
I've only been weighing dry for an experiment that I'm conducting. I've been keeping feeding constant but have not been weighing input.

how many fish, what size or overall size in inches of fish?

If you tell where you're going with this I'll go home and start measuring. Until then here are some pics to give you an idea.
These are the bigger fish:
http://i216.photobucket.com/albums/cc82/Brodersfish/P1050833.jpg

http://i216.photobucket.com/albums/cc82/Brodersfish/P1020519.jpg


overall capacity of enclosed system
Total water volume is about 600 liters. There is substrate in the display, a fairly large DSB, a small mud bed, live rock in the display and an ATS.
Hey.... no need to apologise even if this doesn't go anywhere. Theories are always welcome.

By the way, the necrosis on the staghorn has stopped. Probably due to the heavy waterchanges, which I am still continuing with.

routestomarket
10-23-2009, 02:03 AM
Playing devils advocate I feel that the purpose of an ATS has been somewhat misplaced.

I know this may raise a few eyebrows, however please hear me out.

Talking of my own experience, I set up an ATS with the objective of removing nitrates and phosphates and other dissolved particles by way of algal growth.

Despite being told that my system is poorly design and innefective these objectives have been reached.

Reading through the posts on this site it would appear that the proposed goal of an ATS is to have 2" thick growth over all the screen, not to export waste, and as such it appears there is an algae producing race with the higher yields getting most praise!

Surely common sense would dictate that if you are taking more out of an enclosed system than you are putting in, you are not just exporting the things you want to. Looking at your screens and weekly yield, and assuming undried alage is somewhere equal in water content to frozen food, unless you are putting around 20 full blister packs of frozen food in to your system per week your scrubber is over performing and removing further nutrients / minerals / other, to give you your weekly crop.

In addition to this we must all appreciate the complexity of the algae family and remember fully that no two systems are equal in either thier construction / operation and perhaps most crucial, the type of algae you have growing on your screen.

It is widly regarded that algae was, should you believe in evolution, the first organism on the planet and this type of algae was opposite to those found today in as such as it fed upon CO2 and expelled O2 and due to its increasing biomass converted the planet to what we have today. Also in recent scientific research a type of algae has been found which converts exhausr gasses from a car and produces biodiesel.

I know slightly off topic but the point is no two algaes are the same in thier processes and required foods and as your algae is unique we need to consider is this the problem. Have you, through producing a overly effective ATS created an algae that feeds on other items than the required phophates and nitrogen based waste products of your system.

Might be controversial but I would probably remove a buld or two and see if the desired results of not nitrates, phosphates etc are achieved.

And finally lets not forget the earlier posts and remember that this system is only meant to remove phosphates and nitrates and not the requirements of dosing with minerals etc. just look at Worleys dosing regime:



Only just started recently:
Seachem trace elements once weekly
Seachem Iodide every other day
Seachem buffer and builder as needed
Seachem Reef Advantage Calcium (really great product, increases calcium, but also replenishes Magnesium and Strontium in the ratios they are used up in relation to calcium)

This also raises the question, if already dosing trace elements, incorporating iodide, what is the requirement for additional further dosing of iodide? Perhaps Worley has seen the same problems you are describing or conversely avoided them through the dosing regime.

You mention also that you used to have a fowlr system, what were you readings then? Died you have a phosphate or algae problem back then? If not this would also indicate you scrubber is TOO strong!

Hope this helps or at the very least gives you another avenue of thought! :)

Broder
10-23-2009, 05:27 AM
Your post makes sense, but I don't see how differs very much from what I've been saying. The thing for us to do is to report when we find problems arising. You make some valuable remarks when you say people are not encountering these problems due to heavy supplementation of minerals and trace elements. I just wish we could be more scientific about which elements are depleted the most, and how much we should be supplementing.


Have you, through producing a overly effective ATS created an algae that feeds on other items than the required phosphates and nitrogen based waste products of your system.


Undoubtedly! Plants need the primary macro nutrients potassium, nitrogen and phosphorus to grow. The secondary macro nutrients sulphur, calcium and magnesium are required. The following micro nutrients are required: Boron, copper, iron, chloride, manganese, molybdenum and zinc. These mineral nutrients are surely required by zooxanthellae to grow? Some of these minerals in higher than required amounts become toxic in the aquarium. The algae scrubber surely does a fine job of removing some of them, but can only absorb a proportional amount to the biomass produced. Are we removing enough, not enough or too much of these minerals?

These are the questions that need answering so that we can confidently fend off scrubber criticism when it arises as I'm sure it will. An aquarium will flourish with the correct balance of nutrients. Water changes will go a long way to maintain these balances, but I suspect that we need to supplement some more minerals, other than the usual calcium carbonate that we have been dosing, prior to using scrubbers.

I've heard somwhere that you can tell which minerals are in short supply in the reef aquarium by observing which colours of corals are not as bright as they should be. Does anyone have a link to that?


Might be controversial but I would probably remove a buld or two and see if the desired results of not nitrates, phosphates etc are achieved.
I won't do that as a scrubber will be self regulating. ie. under optimal growing conditions, it'll stop growing when macro nutrients are in short supply. This is what I'm trying to achieve.

Broder
10-23-2009, 08:55 AM
I just went to the last page of Santa Monica's thread and skimmed (excuse the term), through the last updates. It seems that other SPS growers are starting to realise the same thing.

MyFishEatYourFish on the MFK site: "update on my tank. no waterchanges since completion of ats over six months ago with multiple thriving sps, polyps, and a softies. [DT] algae growth is slowed, though what algae does grow is much harder than normal because it is corraline and that crappy tough brown stuff. my plants, chaeto and small grape calerpa show almost no growth, unfortunately xenia grows much slower than i would like too. one thing that everyone skimping on waterchanges must know is to keep up on additives, coral vite, calcium, magnesium, stonium, molebdenum essential elements etc. the best part is my nitrates and phosphates are still undetectable!!! thanks santa monica for starting this great thread!

The slow xenia growth may indicate low iodine. Water changes would reduce the amount of mineral nutrients he has to supplement, and would ensure that he doesn't throw the balance out.

SantaMonica
10-23-2009, 11:42 AM
People have always had slow or no xenia growth with scrubbers. I never could grow them. It's one of the stated drawbacks to scrubbers. Xenia just need too much N and P.

Broder
11-02-2009, 09:03 AM
So I've become the proud owner of a Seachem iodide (the biologically available form of iodine) testkit. I tested the tank after all of the water changes and iodide dosing and found the level to be 0.01ppm(NSW is supposed to be 0.06-0.08ppm).

The good news is that the scrubber comes out clean. How you ask? Well I tested the sea water that I've been using and found the level to be 0ppm, even after tripling the test sensitivity. Anyhow, the coral is recovering nicely and my xenia is pulsing away merrily.

routestomarket
11-02-2009, 09:25 AM
Thought that might have been the problem!

Glad you got to the bottom of this in time for your corals. :D