Originally Posted by TimT (Post 1034427)

To figure that out you need to find out how much water your tank uses on a daily rate and it's daily Phosphate production. Then add the appropriate amount of Foz Down to the ATO reservoir.

For example: Assuming 300 gallon tank heavily stocked with fish with about 240 gallons of water volume.
Tank evaporates 1 gallon of water a day. Reservoir holds 5 gallons.

Morning Phosphate reading of 0.08mg/l

Phosphate reading 24hrs later of 0.12mg/l

Tank volume of 240 gallons of water = 240 * 3.78 = 907.2 Liters

Daily Phosphate production = 0.12mg/l - 0.08mg/l = 0.04mg/L * 907.2 L = 36.29mg of Phosphate produced per day.

1 drop of Foz Down removes 0.04mg/l from 37.8 Litres = 1.512mg of Phosphate.

36.29mg of Phosphate needs 24 drops of Foz Down to neutralize it.

Your tank would need 24 drops of Foz Down per day to neutralize it's Phosphate production.

The ATO reservoir holds 5 days of water so you would add 5 * 24 drops of Foz Down to it.

1 ml is roughly 20 drops so you would add 6 ml of Foz Down.

An 8oz bottle of Foz Down is 240ml. So there is 40 dosages in the bottle. 1 dosage = 5 days so 1 bottle of Foz Down would keep Phosphates down in your tank for almost 7 months. That works out to about 15 cents a day for a heavily stocked 300 gallon system.

Hope that helps.