Can GFO really remove phosphates this quickly?

[Oregon Grown Reef]

Run it 24/7 or you risk fouling water in a container with no flow.
To test if it is exhausted check the tank water & the flow coming out of the unit. Being close or the same means it should be replaced.

I was thinking about running it on a 2 hour timer every day, but then quickly decided against it and will be running it full time for this reason. There were no ill effects from me leaving it off for 16 hours this time, but I don't want to continue to do that.

 

[Skynyrd Fish]

Also don’t drop you PO4 to fast. You can have adverse effects. What is your NO3? Remember this is a balanced relationship. You need po4 to process no3 and vise Versa. Gfo always brought on cyano and even Dinos for me. I now will dose no3 if my po4 is high. If my no3 is not to high. Every tank is different. I would say slow and easy with the gfo. It works for many people.

 

[Oregon Grown Reef]

Also don’t drop you PO4 to fast. You can have adverse effects. What is your NO3? Remember this is a balanced relationship. You need po4 to process no3 and vise Versa. Gfo always brought on cyano and even Dinos for me. I now will dose no3 if my po4 is high. If my no3 is not to high. Every tank is different. I would say slow and easy with the gfo. It works for many people.

My nitrate was at 25 before I started gfo. I haven't tested them again yet, but it seems that number should provide me with a buffer. I can retest here in a bit. It was not my intention to drop it so quickly as I was only following the instructions on the package of gfo. It surprised me how quickly it dropped, hence the title and why I made the thread.

 

[fishybizzness]

Your best bet would be to run maybe 1/2 cup or less and test every other day for a week. If you see your phosphate stabilize then you can just run that much. If it continues dropping just change out to 1/4 cup and continue testing every other day. Once it stabilizes for a few tests, that is the correct amount for your system. Test weekly at that point and once you see your phosphate creeping up then you will know that it's time to change the gfo and refill with the amount you determined previously.

 

[IslandLifeReef]

I would also recommend running less GFO for a while and allow the PO4 to come down a little more slowly while monitoring NO3. I would consider using 1/4 cup for a week and then change it out for another 1/4 cup of fresh GFO. Patience is your friend.

 

[Oregon Grown Reef]

I would also recommend running less GFO for a while and allow the PO4 to come down a little more slowly while monitoring NO3. I would consider using 1/4 cup for a week and then change it out for another 1/4 cup of fresh GFO. Patience is your friend.

I already removed most of the gfo after the levels went down that quickly. I'm running closer to half a cup at this time. I'll test more tomorrow to see where it's at an adjust if need be.

 

[Oregon Grown Reef]

I would also recommend running less GFO for a while and allow the PO4 to come down a little more slowly while monitoring NO3.

What effect should I be seeing on nitrate?

Edit: From my reading, I can't find anywhere that says gfo will remove nitrates nor will the removal of phosphates cause nitrates to fall. I just tested nitrate and it went up the last couple of days, which means some of the alkalinity is "lost" from the rise, but not all of it as the alk lost from a rise in nitrate can be calculated and it wasn't the full amount.

 

[IslandLifeReef]

What effect should I be seeing on nitrate?

Edit: From my reading, I can't find anywhere that says gfo will remove nitrates nor will the removal of phosphates cause nitrates to fall. I just tested nitrate and it went up the last couple of days, which means some of the alkalinity is "lost" from the rise, but not all of it as the alk lost from a rise in nitrate can be calculated and it wasn't the full amount.

You are correct, GFO will not remove nitrates. It is a balance issue though when talking about PO4 and NO3. If you remove to much of either, then your tank becomes limited by the lower of the two. What do I mean by that? Let's say that your NO3 is presently at 25ppm and your PO4 is presently at .2 ppm. There are no other issues and those readings stay fairly consistent. Your tank is probably balanced, and it it processing/consuming those nutrients at the same rate due to the inhabitants and biological filtration. Now, you use GFO to lower your PO4 to 0.04 ppm. Those inhabitants and your biological will still try to consume both, but they don't have as much PO4, so they won't consume as much NO3. Your tank in now PO4 limited and you will either have to dose PO4, or use some other means to reduce NO3 to bring it back into balance. What is the best ratio for NO3 to PO4, hard to tell. I've seen anywhere from 20:1 to 100:1 work well. If your PO4 is 0.04 and you see your NO3 go from 25 to 40, then you have probable brought you tank out of balance and will struggle with NO3. If NO3 stays steady at 25 and everything is happy, then it is probably not a problem. Just my two cents.