static416
Active Member
For a variety of reasons, I have a high bio-load and low coral density at the moment. This means that nutirents are not absorbed as much as I'd experienced previously.
On top of that, I had about 3 months where I barely paid attention to the tank, and the phosphate crept upwards to about 150ppb. That's not catosphrophic, but I prefer it about 20-40ppb.
So I've been trying to lower it with carbon dosing, but it doesn't work well at these levels. In order to keep the phosphate stable at the level I wanted, I needed to dose so much that my ph would hit 7.7-7.8 at night. Actually lost a couple corals due to these ph swings.
Also, repeated ph drops from too much carbon dosing drops my alk randomly.
Core problem turns out to be that the phosphate in the rocks establishes an equilibrium with the phosphate in the water. If you lower the phosphate in the water, more will leach out of the rocks. This can create a kind of rubber-banding of your phosphate level if you dose carbon to lower it. The phosphate will drop quickly with a carbon dose, then leech out of the rocks and rise back a bit.
Turns out that the revolutionary technology I needed was actually just GFO.
I skipped it until now because I had used GFO previously on a smaller tank and it completely wiped out my phosphate. But in this 340gal, it's a much more gradual change.
So now I'm finally stable for a week at:
ph: 8.1 at night and 8.4 during the day
alk: 9.5 dkh
nitrate: 6.5 ppm
phosphate: 40ppb
I imagine that the the amount of GFO I'm using to bring the phosphate down is probably higher than I want in steady-state. But for now things are finally looking good.
On top of that, I had about 3 months where I barely paid attention to the tank, and the phosphate crept upwards to about 150ppb. That's not catosphrophic, but I prefer it about 20-40ppb.
So I've been trying to lower it with carbon dosing, but it doesn't work well at these levels. In order to keep the phosphate stable at the level I wanted, I needed to dose so much that my ph would hit 7.7-7.8 at night. Actually lost a couple corals due to these ph swings.
Also, repeated ph drops from too much carbon dosing drops my alk randomly.
Core problem turns out to be that the phosphate in the rocks establishes an equilibrium with the phosphate in the water. If you lower the phosphate in the water, more will leach out of the rocks. This can create a kind of rubber-banding of your phosphate level if you dose carbon to lower it. The phosphate will drop quickly with a carbon dose, then leech out of the rocks and rise back a bit.
Turns out that the revolutionary technology I needed was actually just GFO.
I skipped it until now because I had used GFO previously on a smaller tank and it completely wiped out my phosphate. But in this 340gal, it's a much more gradual change.
So now I'm finally stable for a week at:
ph: 8.1 at night and 8.4 during the day
alk: 9.5 dkh
nitrate: 6.5 ppm
phosphate: 40ppb
I imagine that the the amount of GFO I'm using to bring the phosphate down is probably higher than I want in steady-state. But for now things are finally looking good.
