And here's another more recent site, that again advises much higher rates of Lev than required.
http://subquaria.com/Levamisole-HCl-Powder
• 10 Gallons Of Water = 0.3 Grams
• 15 Gallons Of Water = 0.5 Grams
• 20 Gallons Of Water = 0.6 Grams
• 25 Gallons Of Water = 0.8 Grams
• 29 Gallons Of Water = 0.9 Grams
• 30 Gallons Of Water = 1.0 Grams
• 40 Gallons Of Water = 1.3 Grams
• 50 Gallons Of Water = 1.6 Grams
• 55 Gallons Of Water = 1.8 Grams
• 65 Gallons Of Water = 2.1 Grams
• 75 Gallons Of Water = 2.5 Grams
• 90 Gallons Of Water = 3.0 Grams
• 125 Gallons Of Water = 4.1 Grams
• 150 Gallons Of Water = 5.0 Grams
• 180 Gallons Of Water = 6.0 Grams
I guess that's a good thing if one is selling the product, not so much if one is using the product and has sensitive fish.
http://subquaria.com/Levamisole-HCl-Powder
• 10 Gallons Of Water = 0.3 Grams
• 15 Gallons Of Water = 0.5 Grams
• 20 Gallons Of Water = 0.6 Grams
• 25 Gallons Of Water = 0.8 Grams
• 29 Gallons Of Water = 0.9 Grams
• 30 Gallons Of Water = 1.0 Grams
• 40 Gallons Of Water = 1.3 Grams
• 50 Gallons Of Water = 1.6 Grams
• 55 Gallons Of Water = 1.8 Grams
• 65 Gallons Of Water = 2.1 Grams
• 75 Gallons Of Water = 2.5 Grams
• 90 Gallons Of Water = 3.0 Grams
• 125 Gallons Of Water = 4.1 Grams
• 150 Gallons Of Water = 5.0 Grams
• 180 Gallons Of Water = 6.0 Grams
I guess that's a good thing if one is selling the product, not so much if one is using the product and has sensitive fish.