I think I will move your thread to Lee's forum to see what he thinks about this product. It's a microbicide used to kill bacteria, mold, yeast and algae. It's dimethyliminoethylene dichloride, ethoxylate. Here is its MSDS.
Emergency Overview
Risk: Harmful to aquatic organisms
Ecological Information
DIMETHYLIMINOETHYLENE DICHLORIDE, ETHOXYLATE
The material is classified as an ecotoxin* because the Fish LC50 (96 hours) is less than or equal to 0.1 mg/l
Manufacturer's website:
Marine
Reef â€"œsafe aquarium algaecide. Controls many types of algae in marine and reef aquariums. Will not harm marine fish, corals and other invertebrates. Will not harm coralline algae. Effectively controls Green algae, “Red Slime,†and “Brown algae†in marine aquariums containing live corals, invertebrates and fish. Use weekly to control algal growth and reduce aquarium maintenance. Does not discolor water or cause foaming.
What exactly do they mean by "reef-safe?" It is a biocide. That means it kills life, including "green algae," "Red Slime" (which is actually cyanobacteria) and "brown algae."
The manufacturer recommends that you use it "weekly to control algal growth and reduce aquarium maintenance." What are the residual effects? The manufacturer probably has no clue because I doubt that any studies have ever been run. This is a product that is an ingredient in wood preservatives used to prevent the growth of bacteria, yeast, mold and algae.
It is toxic to fish, according to the MSDS, at levels less than 0.1 mg/l. I don't know what the concentration is in Algaefix but I'm sure it's quite dilute or you would end up killing everything in your aquarium.
You can't kill stuff without killing stuff. What the manufacturer is trying to get you to do here is add a biocide to your aquarium weekly to kill off nuisance algae and cyanobacteria but at a dosage that the manufacturer believes is harmless to other marine life in your aquarium. How do they know? Did they run any long-term studies?
What are the long-term effects of using this toxic substance in a reef aquarium? Are the toxic effects cumulative? How does it affect the reproductive systems of animals in your aquarium? How does it affect their immunological systems? What are the effects on expected lifespan?
There are NO products that KILL stuff that are COMPLETELY SAFE for use in a reef tank. There are no products that claim to get rid of cyanobacteria that are both completely effective and completely safe for use in a reef tank. The ones that appear to work are not 100% safe. If they were 100% safe, they wouldn't work.