Raising Phosphates

[tnc112105]

I know there are a ton of threads on here already so I apologize in advance for the redundancy.

I am trying to raise phosphates in my tank. I started dosing nitrates a few weeks ago to get them above 0 and in the process I seem to have bottomed out my phosphates. I understand why this happened, and now I need to fix it. To make matters worse, I've been tinkering with the lighting recently because I thought the problems I was having was related to PAR, not nutrients, but that's a different story altogether.

I have been conservatively dosing Brightwell's NeoPhos (6mL/day, ~100 gal tank) for three days and the phosphate has not budged. I understand that the rock/sand is likely absorbing the phosphate which is why my readings are still undetectable with Hanna ULR Phosphorus, in as little as 60 mins after dosing.

My question is this - how quickly can I re dose without causing the opposite problem (and the algae that will surely ensue if I dose too much, too quickly). The bottle says 24 hours, but considering how quickly the rocks are sucking up the phosphate, I could be here a while... If the readings are still 0 after an hour, is it safe to add another dose?

 

[Biglew11]

I dosed about 1.5 weeks before I had detectable readings the next day in a 75.

Using seachems flourish phosphate I dosed once in the morning and once in the evening, using the full dose calculated to get the level I was looking for .1 ppm

You may be able to dose a little faster at first until your rock and sand stop absorbing it.

 

[Randy Holmes-Farley Verified Community Expert]

If the readings are still 0 after an hour, is it safe to add another dose?

Yes. If you believe your kit, as soon as you are below your target level, I'd dose more phosphate.

 

[tnc112105]

Thanks @Biglew11. After you started getting detectable readings and/or reached your target level, did you have to continue dosing phosphate or was regular feeding enough to maintain it? Did you have any issues with algae during or after dosing? I know phosphate absorbtion by the rock and sand is inevitable, but most times you hear about it it seems to be associated with leaching and/or algae issues.

 

[tnc112105]

Thanks @Randy Holmes-Farley! I can double check it against an expired Salifert kit I have, but I don't know how useful that would be. Is it known how quickly rock binds phosphate? It appears to be incredibly fast as the dose I am using should raise the level to 0.02ppm and I am still getting a solid 0 from the Hanna after 1 hour.

Also, should I be concerned about elevating other elements by dosing too quickly? Unfortunately Brightwell does not disclose what type of phosphate salts they use - only that it is a "proprietary blend".

 

[Biglew11]

I started dosing about 3 weeks ago so I'm still dosing. About every other day now, I'm also carbon dosing to get my nitrates down wich is eating my phosphates some.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks @Randy Holmes-Farley! I can double check it against an expired Salifert kit I have, but I don't know how useful that would be. Is it known how quickly rock binds phosphate? It appears to be incredibly fast as the dose I am using should raise the level to 0.02ppm and I am still getting a solid 0 from the Hanna after 1 hour.

Also, should I be concerned about elevating other elements by dosing too quickly? Unfortunately Brightwell does not disclose what type of phosphate salts they use - only that it is a "proprietary blend".

Yes, it is fast. It is exactly like phosphate binding to GFO.

There's no concern what cation is. Probably mostly sodium and a little potassium in a commercial mixed product.