Howdy,
A buddy asked me to review this "home remedy", and I remembered your post. Having done a safety review of it, I thought I'd share that I actually have some serious concerns:
You are right that glutaraldehyde will have the same beneficial effect for plants, but at a considerably higher risk of acute toxicity and not as smart regarding duration of availability, hours after dosing. Excel is the same stuff, just many molecules connected to each other, forming a polymer. That means it acts like a reservoir, slowly allowing light (i.e. photodegradation), bacteria and plants to break it down into usable form. This leads to a steady low level of glutaraldehyde available. Glutaraldehyde is the usable form, and also the toxic form. You add it to the tank, it's like BOOM. High dose right there, bioavailable. The polymer releases it slowly, that's key! If you had crustaceans in your tank, depending on the species, they would die (I calculated the dose from this post and compared to lethal concentration in daphnia). Besides, these concentrations of bolus dose glutaraldehyde are definitely toxic to bacteria, very likely to affect your biofilter with the first couple of doses (might adapt if dosed daily). You sometimes even see a cloudy tank after Excel dosing, imagine that booted. Not a risk I'd be willing to take! Excel is cheaper than my fish...
Lastly, glutaraldehyde is a possible health hazard for you if you don't wear gloves every time you handle it. It's a sensitizer, i.e. at the concentration in this bottle, it is not uncommon to develop allergies against this product. One more reason not to play with it
HarleyK
