Product Review
A Glut on the Market
Is Glutaraldehyde a new “miracle product” for planted aquariums?
By Paul Garrett
In the past few years, several products have been available that purport to replace carbon dioxide as an aquatic plant
fertiliser. They are all, as far as I can tell, based on a chemical called Glutaraldehyde (pronounced glut-ar-al-de-hide),
or “glut” for short. The theory goes that the higher plants (but not algae and not some mosses and liverworts) can use a
complex, organically bound form of carbon (ie. glut) instead of CO 2 when they photosynthesise. Sounds great.
Aquarium CO2 systems are certainly effective (if you have adequate light and the other essential plant nutrients are in
balance) but the compressed gas systems are fiddly and expensive and DIY systems are, in my experience anyway, messy
and unreliable.
These glut products offer a way to ditch those systems and replace them
with a liquid that can be added regularly to the tank along with other
fertilisers – or in one case, a dissolvable block that only needs replacing
every three weeks.
Glut is also recommended, in higher than normal doses, for disinfecting
plants and, specifically, for killing of black brush algae attached to their
leaves. Most aquatic plant keeps would welcome this as “BBA” is such a
scourge and very difficult to kill or even manually remove from plants
once it takes hold.
I have looked at three glut-based products and done a few tests and
calculations.
Note: Concentrated Glutaraldehyde
is toxic and care needs to be taken in its
use. You should avoid skin, and
particularly eye, contact with the
concentrated product and immediately
wash anything that comes into contact
with it. It has a distinctive, pungent
smell. The container (or block) of
concentrated glut should be stored
safely away from children or pets (as
should most aquarium treatments).
The most widely available glut product is “Flourish Excel™” by Seachem. Most good aquarium shops stock it and it is
widely available on-line. The name is bit confusing as Seachem also make a product called just “Flourish™” which is
also a plant fertiliser and there is a range of specific fertilisers also marketed under the “Flourish™” name (Flourish
Nitrogen™, Flourish Phosphorus™ and Flourish Potassium™). They are quite different. “Normal” Flourish™ is a mix