One other thing, is that AF freshwater has been reported to be identical as far as content to the salt water version. I have not seen the label for the freshwater version. You should dose the AF freshwater version per the instructions for the salt water version if they are different. Perhaps you can confirm if both labels are the same?
This is the saltwater AF label:
"Benefits: AlgaeFix marine effectively controls these types of saltwater algae: Green algae (Cladaphora), "Red Loine" (Oscillatoria/Spirulina major), "Brown algae" (Cyclotela) in marine aquarium containing live corals, invertebrates and fish. When used in salt water will not harm snails, clams,scallops, shrimp, anemones, sea cucumbers, feather dusters, coralline algae, soft corals, hard corals and other invertebrates. Does not discolor the water or cause foaming.
Directions for use: It is a violation of federal law to use this product in a manner inconsistent with its labeling. Add 1 ml (1/5 tsp. for each 10 US gallons (38 L) or 5 ml (1 tsp.) for each 50 US gallons (190 L) or 50 ml. (10 tsp.) for each 500 US gallons (1,890 L) of aquarium water. Repeat dose every 3 days until algae is controlled. Siphon or scrape any dead algae from aquarium. Once algae growth is under control, add one dose per week. Weekly doses of AlgaeFix Marine will control Alger growth and reduce aquarium maintenance.
Precautionary Statement
Hazards to humans & domestic animals.
Caution: Harmful if swallowed or absorbed through the skin. Avoid contact with skin, eyes or clothing. Wash thoroughly with soap and water after handling. Note: This product contains a chemical known to the state of California to cause cancer.
First Aid: If on skin, thoroughly wash with soap and water and remove contaminated clothing. If in eyes, hold eye open and gently flush with water for 15 minutes. If Swallowed, call a Poison Control Center or doctor immediately for treatment advice.
Storage and Disposal: Do not contaminate water or feed. Do not reuse empty bottle. Rinse throughly before discarding in trash."