Does dosing nitrates lower phosphates?

bozo · Nov 10, 2023

50 gallon total volume tank

ALK: 7.7
CAL: 450
MAG:1350
NO3: 8.6
PO4: 0.006 ppm. It was at 0.04 ppm yesterday at the same time.

My tank has always had zero nitrates and phosphates since inception. 10 month old tank.

I just started dosing nitrates with Sodium Nitrate on 08NOV2023

I got nitrates up to 9-10 PPM from zero.

To get my phosphates up, I accidentally dumped a crap ton of pellets in the tank a week ago. I siphoned them out into a filter sock and left them there to release phosphates. That got my phosphates up to 0.1 ppm.

As soon as I dosed nitrates to 10 PPM on 09NOV2023, my phosphates went from 0.04 ppm to 0.006 ppm with in 24 hours, today.

I’ve read that dosing nitrates does lower phosphates but I just want to confirm again with you guys.

I will start dosing phosphates to get to 0.1 ppm. I have a bottle of Trisodium Phosphate ready to mix.

Thanks

Randy Holmes-Farley · Nov 10, 2023

There’s no answer to that question in general, but if N is low enough that some organisms are growth limited, then adding N will allow them to grow faster and take up more P.

bozo · Nov 10, 2023

Randy Holmes-Farley said:
There’s no answer to that question in general, but if N is low enough that some organisms are growth limited, then adding N will allow them to grow faster and take up more P.

Thanks Randy

Your logic makes sense.

I'll dose phosphates to 0.1 PPM and see where that takes me.

Where would you keep NO3 and PO4 personally?

Thank you

Randy Holmes-Farley · Nov 10, 2023

bozoreefer said:
Thanks Randy

Your logic makes sense.

I'll dose phosphates to 0.1 PPM and see where that takes me.

Where would you keep NO3 and PO4 personally?

Thank you

I recommend 2-10 ppm nitrate and 0.03 to 0.1 ppm phosphate, with levels above that range better than below it.