Stuff I learned the hard way: Dont use aluminium in your tanks!
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Old 08-06-2014, 12:33 PM   #1
Beherith
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Stuff I learned the hard way: Dont use aluminium in your tanks!


Three months ago I installed about 100w of LEDs (2x 50 watt 7 band grow leds, 4x 10w cool white, all underdriven a tad) onto a piece of square aluminum tubing, and passed the filter's water flow through the tube to cool the LEDs and provide some heating for my 50gal planted tank.

Ignoring all warnings that this is a bad idea, I can now confirm that though the power LED heatsink backing seems to be electrically insulated from the LEDs, they are in fact not completely insulated. There may be some capacitive coupling from the LEDS, and if your power supply is not perfectly grounded, then you can even 'feel' the 50hz mains hum in the aluminum tubing by slowly and gently running your finger along it.

To cut a long story short, after my plants started dying off rather quickly, I took apart the assembly to find some galvanic corrosion on the inside of the aluminum tubing.

Interesting note is that it seems that aluminum is more toxic to plants than to fish, as the fish are still fine, its just the plants that all died rather rapidly.

I now removed the water flow from the tubing, and am running the LEDs at only 50w to reduce the heat.

Stay tuned for more of my hard-headed shenanigans.
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Old 08-06-2014, 12:49 PM   #2
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Aluminum in water will also result in the release of hydrogen gas as it corrodes. If I'm remembering correctly what I read recently.
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Old 08-06-2014, 01:00 PM   #3
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The corrosion of aluminium was not fast enough to get visible hydrogen gas formation, since there was only a very very weak AC current flowing through it.
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Old 08-06-2014, 01:04 PM   #4
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Quote:
Originally Posted by Beherith View Post
Three months ago I installed about 100w of LEDs (2x 50 watt 7 band grow leds, 4x 10w cool white, all underdriven a tad) onto a piece of square aluminum tubing, and passed the filter's water flow through the tube to cool the LEDs and provide some heating for my 50gal planted tank.

Ignoring all warnings that this is a bad idea, I can now confirm that though the power LED heatsink backing seems to be electrically insulated from the LEDs, they are in fact not completely insulated. There may be some capacitive coupling from the LEDS, and if your power supply is not perfectly grounded, then you can even 'feel' the 50hz mains hum in the aluminum tubing by slowly and gently running your finger along it.

To cut a long story short, after my plants started dying off rather quickly, I took apart the assembly to find some galvanic corrosion on the inside of the aluminum tubing.

Interesting note is that it seems that aluminum is more toxic to plants than to fish, as the fish are still fine, its just the plants that all died rather rapidly.

I now removed the water flow from the tubing, and am running the LEDs at only 50w to reduce the heat.

Stay tuned for more of my hard-headed shenanigans.

Thanks.. more stuff to learn......
http://www.plantphysiol.org/content/107/2/315.full.pdf

sorry about the plant loss btw..sometimes it rains when you are "outside the box"..
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Old 08-12-2014, 04:02 AM   #5
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So now I am a little worried.. I just bought an eheim 2217 from craigslist for $30 and the pump cover nipple was broken off. So today I made a repair part using O-rings out of aluminum. Now this is totally isolated from any electrical currents and I can't emagine this corroding much at all over the next 10 years, but what do you guys think??
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Last edited by Rhenerie; 08-12-2014 at 04:03 AM.. Reason: spelling error
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Old 08-12-2014, 04:08 PM   #6
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Never mind I think I answered my own question. I found this older thread with a link to a seachem research project on aluminum oxides. I think I can easily say my application will be fine.
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Old 08-12-2014, 04:12 PM   #7
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....and the algae lived on with the fish...
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Old 08-12-2014, 05:15 PM   #8
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....and the algae lived on with the fish...
There is always a silver lining! Now you won't have to raise a new crop of algae to try to kill.
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Old 08-12-2014, 05:59 PM   #9
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I am confused. Is this an inside joke i am missing or sarcastic criticism? or have nothing to do with my post.

Only trying to learn here.
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Old 08-12-2014, 06:35 PM   #10
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I am confused. Is this an inside joke i am missing or sarcastic criticism? or have nothing to do with my post.

Only trying to learn here.
Most of us find algae to be the monster of the aquarium. It grows under any conditions, survives everything, and stays around to haunt our very existence. In this case even a bad case of aluminum poisoning that killed off the plants left the algae alone. So, my comment was just a joke, based on my hatred of algae.

A very few of the people here actually grow algae on purpose, either to feed certain fish or, in rarer cases, as a decoration in the aquarium.
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Old 08-12-2014, 06:48 PM   #11
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Thanks, Hoppy.

I only asked because I am a little cautious of this aluminum fitting. But every single scientific article I can find says I should be fine in a typical planted tank with 7ish PH. I hear alot of people say otherwise but no evidence.

Even if aluminum corrodes it would be an insoluble oxide from what I am reading. So the OP's situation must have been because of direct galvanic action. That is my assumption. However that still doesn't take away from the fact that I would have rather used an Inert material. Such as Medical SS, nylon or some sort of acetel. But we don't stock any of those materials here so the cost would of outweighed my savings.

Any well founded opinions are welcome. What drew me into aquariums initially was the DIY opportunities available.

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Most of us find algae to be the monster of the aquarium. It grows under any conditions, survives everything, and stays around to haunt our very existence. In this case even a bad case of aluminum poisoning that killed off the plants left the algae alone. So, my comment was just a joke, based on my hatred of algae.

A very few of the people here actually grow algae on purpose, either to feed certain fish or, in rarer cases, as a decoration in the aquarium.
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Old 08-13-2014, 12:27 AM   #12
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Is the aluminum piece that you repaired/replaced the hose nipple thingy? or something else?

If you poke around the plumbing section of hardware stores, a lot of times you can find various plastic hose nipples and such, if that's an option I would probably try that.

And I don't think it's the aluminum oxides that pose a problem, so much as aluminum ions in the water, but it's been a while since I've read much on it.
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Old 08-13-2014, 01:51 AM   #13
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The peice I made, I fabricated on a lathe as a one off part. I also had to modify tbe pump head as eheim chose to make their own unique thread, thats neither imperial or metric. Originally there was a hose barb there with a lock nut. Nipple was broken off and only threads remained. To save on purchasing a new pump head cover and convert the output from 1/2 to 5/8 I rethreaded the cover to 5/8 x18tpi and spun this peice on the lathe with two O-ring groves to seal against the cover.

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Is the aluminum piece that you repaired/replaced the hose nipple thingy? or something else?

If you poke around the plumbing section of hardware stores, a lot of times you can find various plastic hose nipples and such, if that's an option I would probably try that.

And I don't think it's the aluminum oxides that pose a problem, so much as aluminum ions in the water, but it's been a while since I've read much on it.
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Old 08-13-2014, 11:10 PM   #14
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allright, nevermind, if you lathed that yourself, you know far more then I do about any of this stuff.

although I think it would probably better to use some other material (maybe even a plastic?) then aluminum, that's a fairly impressive bit of fabrication there.
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Old 08-14-2014, 03:43 PM   #15
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Wait...you had 50hz? How? Are you saying your rectifier was passing through ripple? That is a problem! Which brand?

For the record, you probably had DC. Electroplating is done with DC. The corrosion was caused by the DC component at least.

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