PO4 dosing but not increasing

[ybotlang]

Hi guys,
my tank has been running at undetectable phosphates for 2 years. For that time I have always struggled to keep good sps colour as they have been starved for nutrients. I have started dosing phosphates and nitrates to get my levels from 0 to something. I have dosed enough phosphates into this tank to increase the levels by 0.25ppm of phosphate. I dosed this over one week and at the end of the week the highest reading I got was 0.01ppm.
Is this normal as I know phosphate can be bound in rocks so is the opposite true where there can be no phosphate bound as there has never been an phosphate in this tank.
Many thanks for any help

 

[Biglew11]

yes if your tank has been running at o phosphates for a while (2years) your sand rocks and other substrate will be totally striped of all phosphates it will probably take a week or 2 to start getting readings 24 hours after dosing. i had to dose 2 a day to .1ppm for 1.5 weeks before i started to get stableish readings after 24 hours.

 

[ybotlang]

yes if your tank has been running at o phosphates for a while (2years) your sand rocks and other substrate will be totally striped of all phosphates it will probably take a week or 2 to start getting readings 24 hours after dosing. i had to dose 2 a day to .1ppm for 1.5 weeks before i started to get stableish readings after 24 hours.

Cheers, I thought that was the case just wanted to double check before I go overboard.

 

[Nick Steele]

I still wouldn’t go overboard on dosing as you’ll reach a tipping point and could overdose. I started with a regular dose to get .03 reading for a week then upped it do get a .07 reading but was testing daily to make sure it didn’t skyrocket. Still could only get a .015 reading so I’m staying there and it is helping the tank.