I went hunting to see if I could track down the basis for the claim on Algaefix Marine labels.
"When used in saltwater aquariums, Marine AlgaeFix will not harm snails, clams, scallops, shrimp, anemones, sea cucumbers, feather dusters, coralline algae, soft corals, hard corals, and other invertebrates."
This statement is EPA-approved, but the EPA documentation on Polixetonium chloride (linked in 1st post) doesn't provide a basis for this.
And it seems a gray area - there are people who use it and find no harm (it's obviously less toxic than in freshwater), but there are others who find it probably did cause harm to inverts in saltwater under some circumstances. (my observed losses with heavy algaefix: 4 out of 4 peppermint shrimp, 4/5 urchins, 2/2 turbo snails, 1/1 montipora, 1/1 sand sifting cucumber, 2/~dozen hitchhiker bivalves)
I found this
interesting document from 2004 where EPA denies API's request to say it's safe for reef inverts.
"General Comments:
Toxicity Studies in Saltwater and Reef Aquaria
While the submitted data did indicate no mortality from treatment with AlgaeFix, several things make the study of questionable scientific validity. Given the concerns in the attached review, the Agency cannot draw any scientific conclusion from the submitted data. Aquatic studies submitted according to OPPTS Guideline requirements have provided sufficient data to characterize Busan 77 as highly toxic to freshwater organisms, ranging from highly toxic to slightly toxic to marine organisms. Since the concentration of the test chemical was not determined in the study submitted with this package, it is unknown whether the level achieved during application according to label directions will approach levels shown to be toxic to marine invertebrates in the Guideline studies.
If you wish to be protective of aquarium organisms such as marine crustacea, further analyses of the concentration of Busan 77 in the water during treatment with AlgaeFix should be conducted to ascertain that it does not approach the levels shown to be toxic to marine invertebrate species in the submitted studies [Mysid, LC50=13ppm (95% confidence interval of 9.1 - 16ppm) NOEC < 7.8 ppm; Quahog clam, LC50 = 350 ppb (95% confidence interval of 0 - 710 ppb), NOEC =230 ppb. Data from published scientific literature may also provide toxicity endpoints for additional species of interest, some of which may be more sensitive than the species tested in EPA Guideline studies."
That was in 2004, but by 2007, apparently additional data had been submitted that satisfied EPA's concerns. The
product label documentation in 2007 contains the familiar approved claim of saltwater safety for inverts.
I say that it must've been additional data, because the EPA still (in 2020) has basically the same low 48hr LC50 for quahog clams - 0.21mg/L.
It's unclear to be how the recommended dose of Algaefix being ~1ppm of active ingredient can square with that unless they showed data that must've said it bonds very quickly and disappears from the water.
Curious if anyone else has seen any data that sheds light on the degree of "safety" for this ingredient in saltwater.
