# My experience with overdosing Metricide 28 (Fluorish Excel, glutaraldehyde) for algae.



## Tiger15 (Jan 7, 2018)

What is the strength of your Metricide. Without knowing the ppm of Glutaldehyde you are dosing, your narrative is meaningless.


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## Oughtsix (Apr 8, 2011)

Tiger15 said:


> What is the strength of your Metricide. Without knowing the ppm of Glutaldehyde you are dosing, your narrative is meaningless.


*MetriCide 28* is a *2.5%* glutaraldehyde concentration --which is what I am using
*MetriCide 14 *is a *2.6%* glutaraldehyde concentration* 

EDIT: Apparently Seachem has changed the concentration of glutaraldehyde in their Excel product to 2.6% and the following is no longer correct.
Seachem Excel *contains a concentration of *1.5% *glutaraldehyde.

So Metricide 28 is 1.67 times stronger than Excel.
Metricide 14 is 1.73 times stronger than Excel.

My tank is 180g. My sump is 55g. I estimate my total actual water volume to be about 200g.


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## jeffkrol (Jun 5, 2013)

You shouldn't use 28 as it contains a surfactant (soap).
Met14 is the usual suggestion.

1ml/gal. is fairly common.
There sre sensitive plants/organisms at those levels (and less part. vals and possibly discus and shrimp)



> Also looking at the msds for both you see that metricide 14 contains only water and glut and metricide 28 contains water, glut and "other ingredients"
> .


Current Excel has the same glut content as 14. Wasn't always the case. Check the bottle.



> I did my research and found that the formula for Excel appears to have changed. Old posts said that Excel was 1.5% Glutaraldehyde. *New Excel label says that its 2.5% Polycycloglutaracetal* , but the dosing instructions remain unchanged:


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## Deanna (Feb 15, 2017)

Metricide 14 is what is typically used WHERE metricide is used. Metricide 28 has surfactants, which are not good for your tank. I prefer Excel, which has no expiration and, since I use it infrequently (usually when I accidentally leave my lights on 24/7 after manually turning them on to clean), I don't use much. I hope you didn't use the "activator" that comes with Metricide. 

Glut generally only kills red algae (various hair algae and BBA) and I would not use it in the way you are. With pressurized CO2, you don't need it for the plants, assuming you can get a 1-1.5 drop in pH with the CO2. I usually recommend 1ml / gal of Excel (I've gone as high a 3ml/gal with no harm to fish, snails and some shrimp) in a single treatment and not repeated for about a week. That would be 180ml of Excel in a 180 gal tank (about .67ml/gal of Metricide 14).

Speaking of surfactants, I noticed that you mentioned you added household ammonia for the cycling. Many household ammonia mixes contain surfactants. You may want to check that before adding any fauna.


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## Tiger15 (Jan 7, 2018)

Based on my calculation, dosing 100 ml 2.5% Metricide to 200g of water is equivalent to 2 ppm Glutaldehyde, which is the initial high dosage recommended by Seachem Excel. If you add another 50 ml to 150 ml, you increased the dosage to 3 ppm Glut, still near Seachem guideline, and well below toxicity level for fish and shrimp.

For your info, I have compiled toxicity test results of Glut from different sources below.

Toxicity of glutaraldehyde
96h acute Bluegill sunfish LC50 = 11.2 mg/L
Bluegill sunfish NOEC = 10 mg/L
48h acute Oyster larvae LC50 = 2.1 mg/L
96h acute Green crabs LC50 = 465 mg/L
96h acute Grass shrimp LC50 = 41 mg/L
48h acute Daphnia magna LC50 = 0.35 mg/L
Daphnia magna NOEC = 0.32 mg/L
96h algal growth inhibition Selenastrum capricornutum ILm = 3.9 mg/L
Algal inhibition Selenastrum subcapitata IC50=1 to 1.8 mg/L
96h algal growth inhibition Scenedesmus subspicatus EC50 = 0.9 mg/L
Bacterial inhibition Sewage microbes IC50 = 25-34 mg/L
96h O. mykiss (Trout hatch rate) IC50 = 1.82 mg/L
96h C. dubia (Daphnia reproduction) IC50 = 4.7 mg/L

*EC=Effective concentration; IC=Inhibition concentration; LC=Lethal concentration;


NOEC=No observed effect concentration


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## Tiger15 (Jan 7, 2018)

Deanna said:


> Metricide 14 is what is typically used WHERE metricide is used. Metricide 28 has surfactants, which are not good for your tank. I prefer Excel, which has no expiration and, since I use it infrequently (usually when I accidentally leave my lights on 24/7 after manually turning them on to clean), I don't use much. I hope you didn't use the "activator" that comes with Metricide.
> 
> Glut generally only kills red algae (various hair algae and BBA) and I would not use it in the way you are. With pressurized CO2, you don't need it for the plants, assuming you can get a 1-1.5 drop in pH with the CO2. I usually recommend 1ml / gal of Excel (I've gone as high a 3ml/gal with no harm to fish, snails and some shrimp) in a single treatment and not repeated for about a week. That would be 180ml of Excel in a 180 gal tank (about .67ml/gal of Metricide 14).
> 
> Speaking of surfactants, I noticed that you mentioned you added household ammonia for the cycling. Many household ammonia mixes contain surfactants. You may want to check that before adding any fauna.


I prefer Metricide 14 over 28 for the same reasons you cited, but 14 was out of stock in my last order so I took 28 instead. I hate the surfactant when I dosed 28 which foamed up for a while, but I don't notice any harmful effects. One item that you should never add is the stabilization agent which is sodium nitrite known toxin to fish. I don't know the reason Metricide instructs adding the stabilization agent in normal usage. 

I dose Metricide to my high tech tanks at the initial high dosage after weekly water change as an algae prevention measure. I don't know if it will make a difference if I stop dosing it since I haven't had algae for a long time, but Metricide has a shelf life of about a year, so if I don't use it up, it will just go expire.


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## Greggz (May 19, 2008)

Tiger15 said:


> I dose Metricide to my high tech tanks at the initial high dosage after weekly water change as an algae prevention measure. I don't know if it will make a difference if I stop dosing it since I haven't had algae for a long time, but Metricide has a shelf life of about a year, so if I don't use it up, it will just go expire.


If you need to dose Glut in a high tech tank, then something is not right.

In a well balanced tank, Glut has no positive impact, and in fact can be detrimental.

You should try not dosing it. You might find the tank is even better


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## Oughtsix (Apr 8, 2011)

I am well aware that Metricide 14 is the preferred mixture for use in aquariums. I could not locate Metriside 14 so I decided to give Metricide 28 a try. I have read countless threads with comments about the surfactants in Metricide 28 and that they are harmful but I could not find a single reference to back up this claim. I could only find someone reciting what someone else told them about Metricide 28. I could find no posts on any of the boards reciting first hand experience with Metricide 28, or even Metricide 14, with any sort of detail. This is the reason I made the post, to add a first hand testimonial describing how I used it and the results I achieved. This wasn't a scientific study, just a testimonial, for what ever a testimonial is worth these days. I am sure no scientific magazine is going to knock on my door asking to publish my account as written but it is more than I have been able to find after some rather extensive internet searching. It is simply a loose record of what I did and the results I observed.

My overflow generates a good amount of bubbles when the tank water hits the sump. I saw no changes in this and saw absolutely no signs of foaming with the concentrations of Metricide 28 I described.

I did not use the Metricide 28 as a carbon supplement for my plants. I can crank up the CO2 levels in my tank to the point that it will fizz if I wanted to. I will be doing some experimentation before I add fish to make sure I do not go over safe levels of CO2. My sole use of Metricide 28 was to kill off algae and it did that... very well... MUCH better and quicker than I had expected! Like I said in my original post my tank is only 3 weeks old. I have other planted tanks and I was expecting an algae outbreak and had the Metricide 28 ready to go when the algae appeared and started to take hold. My tank is not any where near balanced yet and is full of all sorts of great algae promoting compounds.

When I researched Seachem Excel for the last tank I setup it was sold as a 1.5% solution of glutaraldehyde. Apparently Seachem has upped the concentration of glutaraldehyde to 2.5% but made no changes to their dosing recommendations. I have added an edit to my post with this correction.

I have seen no proof that adding Metraside or Seachem Excel on an ongoing basis is harmful to an aquarium. If someone has some reference material about this I would be very interested in reading through the study.



Deanna said:


> Metricide 14 is what is typically used WHERE metricide is used. Metricide 28 has surfactants, which are not good for your tank. I prefer Excel, which has no expiration and, since I use it infrequently (usually when I accidentally leave my lights on 24/7 after manually turning them on to clean), I don't use much. I hope you didn't use the "activator" that comes with Metricide.
> 
> Glut generally only kills red algae (various hair algae and BBA) and I would not use it in the way you are. With pressurized CO2, you don't need it for the plants, assuming you can get a 1-1.5 drop in pH with the CO2. I usually recommend 1ml / gal of Excel (I've gone as high a 3ml/gal with no harm to fish, snails and some shrimp) in a single treatment and not repeated for about a week. That would be 180ml of Excel in a 180 gal tank (about .67ml/gal of Metricide 14).
> 
> Speaking of surfactants, I noticed that you mentioned you added household ammonia for the cycling. Many household ammonia mixes contain surfactants. You may want to check that before adding any fauna.


*"I would not use it in the way you are" *- I do not understand this? I am using it to kill off algae in a brand new tank. Everyone is entitled to their opinion, which is perfectly fine. Do you have any resources that have lead you to this conclusion?

*"Many household ammonia mixes contain surfactants."* I use pure cheap generic household ammonia. Nothing added, I checked the label. I have started up at least 4 tanks with this exact bottle over the years.

*"With pressurized CO2, you don't need it for the plants, assuming you can get a 1-1.5 drop in pH with the CO2."* - I have said nothing (nor have I even decided anything) about long term use of Metricide in my tank.
I will, of course, double check your Delta PH recommendation when I setup my automated CO2 dosing... but this seems like it is inline with what I have read else where, thank you.

I dissolve CO2 in chilled water under pressure to supersaturated levels before I add it to my tank. My automated CO2 dosing will be a bit different configuration than most.



Tiger15 said:


> Based on my calculation, dosing 100 ml 2.5% Metricide to 200g of water is equivalent to 2 ppm Glutaldehyde, which is the initial high dosage recommended by Seachem Excel. If you add another 50 ml to 150 ml, you increased the dosage to 3 ppm Glut, still near Seachem guideline, and well below toxicity level for fish and shrimp.
> 
> For your info, I have compiled toxicity test results of Glut from different sources below.
> 
> ...


Thank you, this was VERY informative! Thank you for doing the math that I was too lazy to do! Since I don't have any fish in the tank and won't for a couple more weeks I just kept upping the dosage until I saw some results. Very unscientific... but it was very effective!  _(My high school chemistry teacher would *NOT *be impressed with my unscientific method!)_



Tiger15 said:


> I prefer Metricide 14 over 28 for the same reasons you cited, but 14 was out of stock in my last order so I took 28 instead. I hate the surfactant when I dosed 28 which foamed up for a while, but I don't notice any harmful effects. One item that you should never add is the stabilization agent which is sodium nitrite known toxin to fish. I don't know the reason Metricide instructs adding the stabilization agent in normal usage.
> 
> I dose Metricide to my high tech tanks at the initial high dosage after weekly water change as an algae prevention measure. I don't know if it will make a difference if I stop dosing it since I haven't had algae for a long time, but Metricide has a shelf life of about a year, so if I don't use it up, it will just go expire.


Yep, that is also how I ended up with Metricide 28. I couldn't find Metricide 14 anywhere that actually had it in stock. The places that advertised it had 30 days or more for delivery. It is almost like there is a world wide pandemic going on or something. I appreciate knowing that others have also had success with Metricide 28 when Metricide 14 was not available.


_I should put the note about the activation agent in my original post incase someone not familiar with Metricide comes across the post when searching. --I will see if I can still edit it. - Note added._


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## Tiger15 (Jan 7, 2018)

Greggz said:


> If you need to dose Glut in a high tech tank, then something is not right.
> 
> In a well balanced tank, Glut has no positive impact, and in fact can be detrimental.
> 
> You should try not dosing it. You might find the tank is even better


My set up is not the norm as I keep dirty cichlid with very high bioload. I have many exposed surfaces of rockscape, filter plastic and glass top that are open to algae attachment even though my healthy plants are algae resistant. One time I stopped dosing glut after my set up was balanced, bba popped up on some hard surfaces so I resumed dosing and never stopped. I am not convinced that glut is a significant carbon source and use it strictly for algae prevention. At the 2 ppm rate, glut is way below toxicity thresholds for shrimp and fish based on reported toxicity test results I compiled. There are lot of scientific data on glut as it is the most widely used biocides and disinfectants. It is very effective against red algae but less so to green filamentous algae. I dosed the same amount occasionally to my zero tech shrimp bowl and it is harmless to my snails and shrimp, but also useless against green spirogyra and clado in it. Glut degrades in 24 hour and has no bio accumulation effect so I feel safe using it prophylactically.


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## Deanna (Feb 15, 2017)

Oughtsix said:


> I have read countless threads with comments about the surfactants in Metricide 28 and that they are harmful but I could not find a single reference to back up this claim. I could only find someone reciting what someone else told them about Metricide 28. I could find no posts on any of the boards reciting first hand experience with Metricide 28, or even Metricide 14, with any sort of detail. This is the reason I made the post, to add a first hand testimonial describing how I used it and the results I achieved. This wasn't a scientific study, just a testimonial, for what ever a testimonial is worth these days. I am sure no scientific magazine is going to knock on my door asking to publish my account as written but it is more than I have been able to find after some rather extensive internet searching. It is simply a loose record of what I did and the results I observed.


Nothing wrong with reporting on your experiences. That is what draws others in to share their experiences and, perhaps, complete a picture.

Regarding Metricide, here is some additional info:

From the manufacturer’s website: Metricide 28 “Contains surfactants”
From the manufacturer’s website: Metricide 14 “Contains no surfactants”

MetriCide™

Regarding surfactants: they are well known to cause problems with fauna (I’ve done it myself). Not all surfactants are bad, although most are and the quantity matters. If you don’t have much, your fish will be fine until w/c’s remove it. If you have too much, they will die. It is, basically, soap. Surfactants reduce the surface tension of water and prevent the fish’s gills from absorbing oxygen.



Oughtsix said:


> "I would not use it in the way you are" - I do not understand this? I am using it to kill off algae in a brand new tank. Everyone is entitled to their opinion, which is perfectly fine. Do you have any resources that have lead you to this conclusion?


By this, I meant that I would simply use a much stronger dose, one time, to achieve the algae knockdown. Perhaps that wasn’t clear in my post.


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## Tiger15 (Jan 7, 2018)

It’s true that surfactant is a physical disinfectant as it can disrupt the surface tension function of cell walls and this is why CDC recommends washing hands with soapy water. CDC also recommends soaking reusable cloth mask in soapy water for disinfection. Foamy water can also coat and disrupt gill function of fauna. But the impact depends on the dosage. When I used Metricide 14 the first time, I was concerned and watched the response of my fish carefully and ready to do large water change to reverse the effect. But the dosage was low and foaming was mild and dissipated soon after the filter was running. I have done it 10+ times and don’t notice any negative effect so I feel safe to continue. But I much prefer Metrice 14 without the surfactant. I cannot find any MSDS on the surfactant so I assume it is no difference from household surfactant that contains no hazardous chemicals. The most likely chemicals could be nutrients such as phosphate in the break down products.

It is interesting to learn that Seachem increased the % of Glut from 1.6 to 2.5 in the Excel formulae suggesting that it is safe and more effective to use higher dosage. I and many aquarists have experimented with higher dosage and have not found any negative effect suggesting the recommended dosage is conservative, as evidenced from the toxicity test data I compiled.


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## Sam the Slayer (Dec 18, 2019)

All that build up and no pic! Lol

I guess the point of your first post was to share your experience and ask others thoughts on it? I have found the lifecycle of the algae’s mentioned to be fairly similar to my experiences in setting up tanks and not using glutaraldehyde. Love the detail of your post though. 


Sent from my iPhone using Tapatalk


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## jeffkrol (Jun 5, 2013)

Tiger15 said:


> But the dosage was low and foaming was mild and dissipated soon after the filter was running. I have done it 10+ times and don’t notice any negative effect so I feel safe to continue. But I much prefer Metrice 14 without the surfactant. I cannot find any MSDS on the surfactant so I assume it is no difference from household surfactant that contains no hazardous chemicals. The most likely chemicals could be nutrients such as phosphate in the break down products.


I've never had Met14 foam even w/ 1ml/gal doses. Didn't add the activator (little bottle that should be discarded) did you?


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## Oughtsix (Apr 8, 2011)

Sam the Slayer said:


> All that build up and no pic! Lol
> 
> I guess the point of your first post was to share your experience and ask others thoughts on it? I have found the lifecycle of the algae’s mentioned to be fairly similar to my experiences in setting up tanks and not using glutaraldehyde. Love the detail of your post though.
> 
> ...


Sorry! 

About the time of my first post in this thread:









About a week ago:









I can't share a more recent pic because the super red ludwigia grew to the top of the tank and received a REALLY bad haircut! It will need to recover a touch before I post another pic.

There has been a bit of green dust algae on the glass that I just wipe off with a rubber squeegee... but that is with 14 hours of high lighting a day.


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## Sam the Slayer (Dec 18, 2019)

Pretty tank! I could see Glutaraldehyde being useful with the amount of plants you have. I think you would find less of a need for it with a more densely planted aquarium. 

I’m loving the red of the hra?! 


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## Tiger15 (Jan 7, 2018)

jeffkrol said:


> I've never had Met14 foam even w/ 1ml/gal doses. Didn't add the activator (little bottle that should be discarded) did you?





Tiger15 said:


> It’s true that surfactant is a physical disinfectant as it can disrupt the surface tension function of cell walls and this is why CDC recommends washing hands with soapy water. CDC also recommends soaking reusable cloth mask in soapy water for disinfection. Foamy water can also coat and disrupt gill function of fauna. But the impact depends on the dosage. When I used Metricide 14 the first time, I was concerned and watched the response of my fish carefully and ready to do large water change to reverse the effect. But the dosage was low and foaming was mild and dissipated soon after the filter was running. I have done it 10+ times and don’t notice any negative effect so I feel safe to continue. But I much prefer Metrice 14 without the surfactant. I cannot find any MSDS on the surfactant so I assume it is no difference from household surfactant that contains no hazardous chemicals. The most likely chemicals could be nutrients such as phosphate in the break down products.
> 
> It is interesting to learn that Seachem increased the % of Glut from 1.6 to 2.5 in the Excel formulae suggesting that it is safe and more effective to use higher dosage. I and many aquarists have experimented with higher dosage and have not found any negative effect suggesting the recommended dosage is conservative, as evidenced from the toxicity test data I compiled.



Sorry, I have mis quoted it in my post. Met 14 has no surfactant. Met 28 has. I always used and preferred 14, but in my last order, 14 was out of stock everywhere. There are other brands of Glutaldehyde that contain surfactant and even citric flagrant that are unneeded.


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