Junior Poster
Nov 7, 2007
I can find a bunch of forum posts and articles of people using straight glutaraldehyde instead of Excel, but no one seems to follow up on the results, dosage sizes, etc. or maybe I just need to improve my search skills.

From what I can gather from the Excel MSDS, straight glutaraldehyde should work just fine, but what I can't find is the concentration of polycycloglutaracetal in Excel. Wikipedia says glutaraldehyde concentrations as high as 5.0ppm won't harm fish, but I'd still like to figure out what the recommended dosage of Excel equates to when compared to a 25% glutaraldehyde / 75% H2O or similar solution. Seachem is pretty mute on the subject so does anyone know this, or where to figure it out.

Sterilization grade glutaraldehyde is pretty easy to find:

Cold Sterilizat - DE Glutaraldehyde / Gallon - 28 Day - New York Tattoo

Gallade Chemical Shopping Cart

Tom Barr

Staff member
Jan 23, 2005
Buy a test kit for Glut and measure it:cool:
Then you will know.
Breaks down fast, with a 1/2 life of about 8-12 hours.

BTW, at higher concentration it's extremely toxic and can cause irrepairable eye damage. My advice is to buy Excel in large amounts if you plan on using it. It smells really intense and is so toxic at higher levels, some fool hobbyist will go blind or do great harm to themselves trying to save 10$ a gallon.

Unless you need like 55 gallon barrels, it's not really economically worth while.

Tom Barr


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
Drs Foster and Smith have regular sales on Excel too. My last 2 liter purchase, a few days ago, cost less, with shipping, than Big Al's did. It seems to me that unless you can get a gallon of glutaraldehyde for around $5 plus shipping, you aren't saving enough to give this a second thought. And, Excel is not glutaraldehyde, even if that is the active ingredient in it.


Junior Poster
Aug 5, 2008
'Polycycloglutaracetal' and glutaraldehyde for plants

Having recently stumbled across various discussion threads relating to the use of Glutaraldehyde in the aquarium to promote aquatic plant growth, I thought I would research the topic a little more for my own edification. This is what I came up with. The commercially available product by Seachem called Flourish Excel TM has a rather oddly termed compound called ‘Polycycloglutaracetal’. Based on the curiously formulated name, it appears that Seachem just made it up to describe a concoction of aqueous Glutaraldehyde with one or more chemicals of undisclosed nature. It therefore follows, that you will not find this fictitious compound on any MSDS or official chemical register of compounds. Of course it is widely known that glutaraldehyde has algicidal properties at specific concentrations, along with uses as a fixative for electron microscopy. Glutaraldehyde is a small compound made up of a short carbon chain with an aldehyde functional group at each end. The chemical formula is HCO-(CH2)3-CHO. The terminal aldehyde groups are quite reactive and in aqueous (i.e. in water) form (> pH 7.0) glutaraldehyde molecules readily forms cross-links to form polymers of varying length. These oligo-/polymers also readily combine with nitrogen groups in proteins to form additional cross-links. Hence, this is the likely origin of ‘Poly-‘ and ‘–cyclo-‘ in the name ‘Polycycloglutaracetal’; the rest of the name is self-evident. So, as it would appear, Seachem has formulated the name to describe the behaviour of glutaraldehyde in water with the additional of some type of protein or other organic compound. The polymerisation capacity of glutaraldehyde to proteins is widely used in biomedical fields in regeneration of collagen and ligaments. Moreover, cross-linking of aqueous Glutaraldehyde with proteins involves more than a dozen different forms (e.g. isomers) depending on solution conditions (e.g. pH, temperature, etc.). These isomers are in equilibrium, so whatever isomer predominates in solution will depend on ambient conditions, and appears not to influence the beneficial net effect of the compound to plant growth. The figure provided by Seachem to describe the general structure of ‘Polycycloglutaracetal’ also corresponds well to the rationale proposed here (see SLW [plants first,... fish will follow


Hi all,

I've tested glutaraldehyde in my aquarium for more than 10 months. The following picture was taken at 37th week of the experiment. But this tank was torn down and turned into NPT 5 months ago.


A few chinese hobbysists have tried high concentrations of glutaraldehyde to kill both algae and fish infections. The algaecide effects were positive, but the antibiotic effects were controversial.