Interesting. I did not know AquaShade was classified as a herbicide. I've never seen it actually kill any weeds and I thought blocking sunlight was its only function. Last time I went to buy it at Rural King they had some other brand on sale for $18.something a gallon so I bought 2 gallons. It looked like Aquashade and colored the pond the same. They also had it in black dye and I wondered if that might work even better.
By EPA's definition, a "pesticide" is any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest - regardless of the means by which it accomplishes the intended function. All "herbicides" fall under the umbrella term "pesticides", but the term "pesticide" also encompass all other "cides" (insecticides, fungicides, rodenticides, miticide, bactericide, etc).
As for lake-colorants, only two brands are EPA-registered as a herbicide/algaecide; AQUASHADE and ADMIRAL. All others lake colorants, of which there are many, are "legally" marketed/promoted strictly for aesthetic purposes.
Beware of comparing lake-colorants based strictly on their cost per gallon. You're basically buying a gallon of fluid that contains an undisclosed amount of pigment (dye-content). Although all lake-colorants are "concentrated", their degree of concentration varies widely - and you won't be able to tell the difference without conducting side-by-side dilution-comparisons under relatively tight controls.
I recently discovered another means for conducting a preliminary lake-colorant comparison, as shown in this short
VIDEO.
Guess which of the two colorants is cheaper, yet takes almost 3X the dose of the other to yield similar levels of coloration after two weeks of sun-light exposure (sunlight causes photo-degradation of dyes).
