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If I have done the math right (I probably have not ) then a 30 ml dose of 2% solution in 60 gallons is .26mg/l, pretty low on their "toxicity scale". That would lead me to belive that the most sensative organisms would be affected. Higher dosing woudl robably affect shrimp or snails, and lastly fish.

Using the same math, 5ml in 10 gallons is about .3mg/l. As I said though, I may not have converted to mg in a 2% solution correctly. I based my figuring on 100g/mol, or 10^5 mg/mol and assumed that one could figure a 2% mol solution in 1liter H2O. Please tell me if I am wrong.

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not sure if I follow how that relates, though it is amusing. If you are refering to using Excel as an "algae repellent or algaecide, that's not my intention. I really like excel but is very expensive in any quantity. If glutaraldehyde is an economical substitute, I'm all for it

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Cool, I was right; though I see I took a more complicated path to get there. As for the calculations for 10 gallons, I was assuming 8.5 gallons since the standard 10 gallon tank is only about 8.5.Assuming the 2% is weight-by-volume: 2% w/v = 2 grams / 100 mL

30 mL in 60 gallons:

(2 grams / 100 mL) * 30 mL = 0.6 grams in 30 mL of the 2% solution.

If you add it to 60 gallons of water, 60 gallons * 3.78 L / gallon = 226.8 L

0.6 grams / 226.8 = 0.26 mg/L

5 mL in 10 gallons: (Still 0.26 mg/L since the solution volume and tank size are both 5 times smaller)

(2 grams / 100 mL) * 5 mL = 0.1 grams in 5 mL of the 2% solution.

Adding it to 10 gallons = 37.8 L

0.1 grams / 37.8 L = 0.26 mg/L

Allan, could you share where you ordered it from since obviously you had a safe and easy transaction?

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I have also seen some listed as "activated". Does that make any difference?

Allan, what brand do you have? You can even PM me if you want.

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Cidex activated Dialdehyde solution info can be found here:

http://www.safety.vanderbilt.edu/pdf/hcs_msds/Cidexactivated_09_05.pdf#search="Cidex"

From what I can tell, the activated means it has a higher pH, probably for better microbe killing. I don't know. The shelf life appears to be "chemically stable" under proper storage, ie 59-86degrees F. This product contains 97.45% water and 2.55% gluteraldehyde by weight.

I wonder if it makes a difference to our purposes if it is activated or if the day use applies to use or to re-using it stuff in a medical setting?

Now to see about pricing/shipping.

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Their boilogical grade looks more economical at 450ml 25% for $15. The equals 4.5 liters at 2.5% dilution. Since the other gluteraldehyde they ofer is pure for EM fixative, I would imagine that the steralization stuff marketed for hospitals/doctors is biological grade. Maybe not though.

With shipping, probably 6-8 buck your talking about $5 a liter. 'Course, for $1.50 more you can get 450ml of 50% solution, or 9 liters of 2.5%, or $2.66 a liter. Excel is $38 plus shipping for 4 liters. IF you want smaller amounts of Excel, it is way more expensive....$7.50 for 500ml plus shipping.

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OCHCH2CH2CH2CHOAfter looking in the CRC handbook for possible polycyclo compounds, I'm guessing the side-chains in the polycycloglutaracetal (active compound) of Excel seems to make it less toxic. Not sure if the cyclo side chains actually allow for more carbon molecules per molecule of the polycyclo compound, but it makes the compound less toxic and/or prolongs the shelf-life.

I would think so, logically. It would seem that activation would kick off an H or OH, possibly then forming longer chains through a C=C double bond. This should make it more stable and less toxic, plus more alkaline?

Yes, no?

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Well that online source really paid off, so to speak. I ordered the 450ml of 25% biological grade gluteraldehyde on Friday around 4:30. It cam today, Wednesday, before noon. The total with shipping was 21.95, so about $6 shipping. That will equal 4.5 liters of 2.5% solution, at $4.88 a liter. If I dose 7ml a day this will last me almost 2 years Not bad.

Thanks for pointing out this source!!!!

Since I have riccia as a major part of my scape, I think I will start around .1mg/l and see what the results are like. For my application, my 29 gallon aquarium (actually 25 gallons) is equal to 94.5L. Making a 2.5% solution by adding 10ml 25% gluteraldehyde to 90ml H20 and dosing 5ml of that solution will give me .13mg/l in my tank. This is convenient since I have a used 100ml Flourish Excel bottle laying around. Also useful since I can do a half dose to my 15 gallon for the same concentration.

I'll post when I am able to see results, either good or bad.

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Ummm, why am I figuring this wrong?Assuming the 2% is weight-by-volume: 2% w/v = 2 grams / 100 mL

30 mL in 60 gallons:

(2 grams / 100 mL) * 30 mL = 0.6 grams in 30 mL of the 2% solution.

If you add it to 60 gallons of water, 60 gallons * 3.78 L / gallon = 226.8 L

0.6 grams / 226.8 = 0.26 mg/L

(2g/100ml)*30ml = 0.6grams in 30 ml at 2%

0.6g/226.8L= 0.002646 g/L

multiply that by 1000mg/1 gram= 2.65mg/l

Why were you getting 0.26mg/l? Where am I doing that wrong?

Another example:

2.5% solution (what i have) is 2.5gram/100ml, or 25000mg/l.

1ml of that solution is 25mg/ml. Adding 25mg to my aquarium, ~100L, is .25mg/l for my aquarium? Is that math correct?

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That could be a bit hard to control in a normal tank, but in my case I have 3 groups of riccia rocks. Group front left, group front right, group in the middle. Only the middle grouping was effected by the glut application and I assume this is due to eigher the highe rlight this group gets, or the fact that I apply the glut in the front right corner, so maybe that is where it settles first.How are you adding the glutaraldehyde to the tank? Maybe if you had enough riccia, you could do a few experiments.

Have thse following groups of riccia:

1) Free-floating

2) Tied to a rock closest to the area where you dose your glutaraldehyde

3) 6 inches away from rock #2

4) 6 inches away from rock #3...and so on so forth.

This way, we can see if the initial "shocking" concentration of glutaraldehyde has anything to do with its death, or if the overall concentration of ~3.75ppm is enough to do it in. If we can figure out what's actually killing it, we might be able to find a good way to dose the glutaraldehyde. ie: Maybe mixing it with new water during a WC and adding it that way, or adding it as the water flows in from a python or something similar.

What is interesting is that a 15ml dose (3.75mg/l) did not really knock out the BBA or all the riccia. Only some riccia was affected and the only BBA hurt seems to be what I directly applied the D'cel to with a syringe at the last WC. I have not changed the CO2 levels though 2 weeks ago I increased the dosing of all my other nutrients. In the past larger doses of Excel would make the BBA turn pink, in this case, only direct application seems to do that. It does seem though that there is no new algae forming, which seems like a promising sign since I did not change the CO2 levels. I added a few Amano's a couple days ago, so we'll see if they pick at any possibly unknown weakened algae.

Is my math right now-> 15ml of a 2.5% solution in 95L=3.75ppm?

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I don't think we'll ever find out how much is in excel, and understandably so.

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Algae is definately receeding. Concentrations that I have described are only detrimental to the algae with direct application though I am noticing that no more algae is returning and CO2 levels have remained the same. However, I increased the dosing of every other nutrient so that may play a part also.

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100ml + 400ml is 500ml. 100/500= 0.20 0.2x25%(original concentration)=5% solution of glut.

5% is that same as saying 5ml/100ml H20. Since gluteraldehyde is ~ the same weight (density) as water you can safely assume 5% is the same as 5g/100ml, or 50mg/ml

So, providing I have done the math right (not my strongest field), and assuming that a 20gallon is really 20gallons (75liters). Dosing 10ml of your solution is: 10ml x 50mg= 500mg/75l= 6.67mg/l!

For more on the math see post 46, 47, 52 & 53 of this thread. That's a pretty high dose! I experienced a high die-off of

In my experience, the DIY version seems to have some added benefit but its not quite as good as Excel. I read receintly what the concentration of Excel was, though I don't remember now. Maybe 2-2.5%, IIRC. So ml per ml, DIY vs. Excel, your concentration is about double.

Let us know how it goes.

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For what it's worth, I still occasionally use the gluteraldehyde I bought a few years ago. I do not dose the whole tank but will spot apply it with a syringe to any nasties I don't like, especially on hardscape. It still seems to have its potentcy. I do not store it in the fridge but in a dark drawer of my desk. I dose straight from the bottle. I suspect that since I do not use it very often, the bottle is not opened enough to allow a serious degradation of the material. I may be wrong though.....

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