How to lower Phosphate?

Phosphate can be lowered by several commercial adds which contains Aluminum or Iron Oxide (GFO). Both are substrate which must be placed in a bed filter. (with the water streaming up).

In this tube water pas through the media exchanging one PO43- with three OH1- ions.

We use Iron Citrate to control phosphate because it work instantly in the water column. No need to pass through the reactor (tube) to exchange PO4 anymore.

The Iron solution contains Iron (II/III) Hydroxide:

The Fe(OH)3 will exchange his OH1- ion with PO43- , 3x OH1- released 1x PO43- ion is being absorbed.

Fe(OH)3 + PO43- => FePO4 + 3OH1-

FePO4 is precipitated and will be skimmed off, or filtered out by the power filters. It can be recognized by de rust (orange) color in the filter wool and in the skimmer.

Sometimes the Precipitation can be recognized by a haze, which stay for about 2-4 hours.

When using Iron Citrate never dose over 0,15ppm at one time (measurable 30 minute after dosing). Iron measurement will half within 6 hours and after 24 hour less than 0,02ppm is measured. Use the DSR Calculator to calculate the dose.

Some Tang’s, Butterfly’s, Angelfish and Tridacna clams can be extremely sensitive for high doses of iron. For this reason you need to explore the level which they accept carefully. They seem to adapt after a time.

We recommend to start with:

day1 = 0,03ppm

day2 = 0,06ppm

day3 = 0,09ppm

day4 = 0,12ppm

day5 = 0,15ppm max. dosing/day

For a faster dosing schedule (very high PO4, > 0,64ppm)

day1 = 0,03ppm, after 12 hours another 0,03ppm

day2 = 0,06ppm, after 12 hours another 0,06ppm

day3 = 0,09ppm, after 12 hours 0,06ppm

day4 = 0,12ppm, after 12 hours 0,03ppm

day5 = 0,15ppm max. dosing /day

To  translate ppm to ml for you tank, use the DSR Calculator.

Fill in the volume,  iron measures value 0ppm (0%), target value 0,15ppm (100%) (or any other target value you wish).

At all time carefully watch the fish behavior.

To use Iron as trace element only, dose <0,05ppm to the aquarium one to twice a week. (watch your phosphate not to drop below 0,02ppm)

Happy Reefing


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