algae scrubber/heavy metals
 

Adey's book cites an experiment in which he placed a stainless steel plate in a seawater ecosystem, measured high concentrations of heavy metals, and then used an algae scrubber to bring levels back to "normal seawater values". He also reports much greater efficiency of algae compared to macroalgae. The documentation is not sufficient.

The Eco-Wheel is a very large area algae scrubber, and a number of tanks now have them. I was interested in how well these tanks might be doing with their heavy metal levels. Additionally, adding iron would stimulate algae growth and uptake of heavy metals as well as phosphorus if needed.

I talked to Chris Owens of Aquatic Engineers about this. It would be intriguing to get some comparative data on macroalgae tanks and algae scrubbed tanks, with and without iron additions, and publish the results.

Your thoughts about this would be appreciated.

Charles Matthews

Yes, I agree that would be interesting. Macroalgae growth (Chaetomorpha and Caulerpa racemosa) does not appear adequate to reduce copper in my tank below about 10 ppb, but turf algae may be different (or not). I don't know of a reason to assume that turf algae will be better, but it just might happen to be true.

Regardless of how much surface area of turf one had, I don't think it could grow too much more rapidly than my macroalgae in terms of mass per day because the nutrient levels in my tank are reduced fairly far by the macroalgae, leaving little extra for additional growth by a more efficient organism. But their biology may be such that they are more likely to take up metals than either of the species that I use.

algae scrubber/heavy metals
 

Randy: the tank with growth limited by nutrients and copper levels you report, I assume that this is also the tank that you are adding iron to?

When you began adding iron, do you know if the copper levels dropped? When you add additional iron now, is there a further reduction in copper levels, with or without associated macroalgae growth?

Also, I am wondering what element is limiting here-presumably phosphorus? I wonder what additions of phosphorus would do to copper, and growth of macroalgae and zooxanthellae/corals? A plant tank aquarist would probably add the limiting agent here.

In any event, I am interested in arranging a test of the algae scrubber, and of Adey's original work. Can you recommend a procedure for getting some samples tested- perhaps an initial testing of copper levels in a limited number of Eco-Wheel tanks? And the approximate cost per test, if you know? I'm interested enough to sponsor this if it provides useful information.

Thanks!



I have another

In any event,

the tank with growth limited by nutrients and copper levels you report, I assume that this is also the tank that you are adding iron to?

Yes.

When you began adding iron, do you know if the copper levels dropped? When you add additional iron now, is there a further reduction in copper levels, with or without associated macroalgae growth?

I have not measured copper until recently, so I don't know what it previously was. I add iron once or twice per week, so I wouldn't expect copper fluctuations (or maybe not even macroaglae growth fluctuations) on that time scale, but I've never tried to measure it.

Also, I am wondering what element is limiting here-presumably phosphorus? I wonder what additions of phosphorus would do to copper,

I don't know. It might be nitrogen, phosphorus, or maybe even a non nutrient like space, light, etc.

That's an iunteresting concept: adding pure nutrient chemicals to spur algae growth that in turn take down metals levels. Of all the suggestions that I've heard, that might be among the most likely to be useful, inexpensive, and with little in the way of potential side effects.

Can you recommend a procedure for getting some samples tested- perhaps an initial testing of copper levels in a limited number of Eco-Wheel tanks? And the approximate cost per test, if you know? I'm interested enough to sponsor this if it provides useful information.

It's not cheap.:( Check out ENC labs:

www.enclabs.com

algae scrubbers/heavy metals
 

Randy: about nutrient addition to increase heavy metal uptake, blue-green algae will fix nitrogen. Adey makes the point that, as nitrogen levels fall to seawater values, there is a succession of species on the scrubber to blue-greens as they begin to fix nitrogen. I have not worked with scrubbers myself yet, but this seems reasonable, so I presume nitrogen would not be limiting. With the enormous number of species available for competitive succession, one might be hopeful that selection would occur to possibly select for optimal species for uptake of limiting phosphates and heavy metals. Since it appears that iron is not limiting in your tank now for driving heavy metals down further, it would be nice if levels of heavy metals could be driven downward without the additions of nitrogen (which might raise nitrates). On a scrubber which had reached a blue-green dominance consistant with low nitrogen levels and measured low phosphates, addition of iron, silicate, iodine, and phosphate in a tank with a large scrubber might be optimal.

I'm going to suggest to theEco-Wheel people that they submit some test data to the lab you suggested, without fertilizer initially to try and replicate Adey's data- possibly in collaboration with him- and to the Inland Aquatics people. They have a lot to gain by this if it works.

Similarly, I am wondering if there would be commercial motivation by the Ecosystem people to submit data, without and with fertilzation, to try and solve this problem.

This gets at a general problem of lack of experimental method in this industry- which you and some of your colleagues have been working hard to solve. I am wondering whether an article defining the heavy metals problem as something of a challenge to the aquatic plant filtering manufacturing community, requesting independent data about this, might be achievable. An effort to to force manuracturers to begin respond to fundamental questions, well formed and posed by aquarists, is needed. Perhaps we should be doing more than talking about this.

To summarize

1) More experimental method is needed. Rather than leave this on the backs of yourself, Shimek, Bingman, and a few others, it might be possible to form a committee through Reef Central to submit well-formed questions such as this to manufacturers and request independent research. Such manufacturers would be recognized as supporting research.

2) I am going to contact Eco-Wheel about the requested copper levels. If they are not willing to subsidize it, I will do so. Water samples may be best sampled from an independent aquarist.

Thanks for your thoughts!

Charles

I have not worked with scrubbers myself yet, but this seems reasonable, so I presume nitrogen would not be limiting. \

If you use a refugium with one or two species of macroalgae, you may not have these succession effects.

I'm going to suggest to theEco-Wheel people that they submit some test data to the lab you suggested, without fertilizer initially to try and replicate Adey's data- possibly in collaboration with him- and to the Inland Aquatics people. They have a lot to gain by this if it works.

:thumbsup:



Perhaps we should be doing more than talking about this.

Depending on how initial results look, the various parties will want to play up or play down aspects that make their products look good or bad. It's a tricky issue.


it might be possible to form a committee through Reef Central to submit well-formed questions such as this to manufacturers and request independent research. Such manufacturers would be recognized as supporting research.

If they would do it, that would be great.:)

Algae (especially the red ones) consume a lot of heavy metals from the water.Most important is arsenicum.Fish likes to eat a lot of plants rich in arsenicum thats why garlick is used as a feeding stimulent.Altough the garlic isnt a marine plant,it contains a lot of arsenicum just like somme marine algae.We add a lot of arsenicum into our aquarium along with the food and even though marine organisms are tolerant to high ammounts of arsenicum in the water(Ron Shimek measured regular salts we use and discovered levels of arsenicum 10 times higher than normal in freshly made saltwater) i still suspect that extremely high arsenicum concentration is offten the cause for tank crashes of old aquariums.