I think I need to start dosing phosphate but I'm afraid!

[Ciwyn]

So my 300 gallon reef has been up and running for almost 1.5 years. The cycle was quite normal and I started introducing fish and coral about a month in. There was very little nuisance algae in the young tank, however cyanobacteria came on pretty strong after about 3 months. I blacked out the tank a few times and now it is very sparse if visible at all. My sand bed is still looks dirty which I would like to fix eventually but I am also not terribly worried about. I think as the system continues to mature it will be alright.

Now the odd part about the tank after the cycle finished was my nitrates climbed up to about 85 and my phosphate dropped to zero (phosphate was definitely present during the cycle). After a few more months of high nitrates and zero phosphate with little success using water changes to reduce the nitrate I decided to try dosing phosphate. I believe my error with that was at one point I was dosing too much of the phosphate supplement a day and raised my phosphate too quickly from 0 to 1.1 (hanna checker normal range) in about 2 weeks it looks like. This caused a lot of my coral to die during that period. Prior to this a lot of the coral was doing well and growing SPS, LPS and zoas. The problem I was trying to correct was the rampant cyano outbreak.

As my tank stands now everything is stable. I have a few acropora colonies growing, euphylia are doing great, as are zoas. I struggle to keep and montipora or seriatopora though. My theory is they don't like the higher nitrate. Nitrate is still at about 85. I had an ICP test done and it showed 70 nitrate and very trace phosphate at 0.02. The ATI test actually recommended adding phoshorus.

Now the nitrate level isn't panicking me. However, I would much rather get it down to a more reasonable level of 5-10ppm. Also having a detectable amount of phosphate in the tank would also be a good thing my target would be about .05. My thought process is if I were to dose phosphate properly to reach that level that would balance the system out and the Redfield ratio I have learned a bit about would bring the nitrates down. My concern is the bad experience I had with a lot of coral die off last time I tried dosing phosphate.

So is my fear unwarranted with attempting to dose phosphate again? The lack of phosphate in the tank is quite confusing to me. I have what I would consider a medium bioload of about 15 fish and I feed them 4-5 times a week.

 

[motortrendz]

I would really be trying to get nitrates down, since your po4 isnt actually zero using seachem flourish to.dose very small amounts a few ml at a time to get it up slightly is all you need.

You may want to start looking into vodka dosing. It really helped me get my nitrates under control and it really doesnt affect the po4

 

[Ciwyn]

I would really be trying to get nitrates down, since your po4 isnt actually zero using seachem flourish to.dose very small amounts a few ml at a time to get it up slightly is all you need.

You may want to start looking into vodka dosing. It really helped me get my nitrates under control and it really doesnt affect the po4

I actually tried vodka dosing for about 6 months (tried vodka and NOPOX). Never saw the nitrates budge, so that method doesn't seem to work very well for me.

 

[Dan_P]

So my 300 gallon reef has been up and running for almost 1.5 years. The cycle was quite normal and I started introducing fish and coral about a month in. There was very little nuisance algae in the young tank, however cyanobacteria came on pretty strong after about 3 months. I blacked out the tank a few times and now it is very sparse if visible at all. My sand bed is still looks dirty which I would like to fix eventually but I am also not terribly worried about. I think as the system continues to mature it will be alright.

Now the odd part about the tank after the cycle finished was my nitrates climbed up to about 85 and my phosphate dropped to zero (phosphate was definitely present during the cycle). After a few more months of high nitrates and zero phosphate with little success using water changes to reduce the nitrate I decided to try dosing phosphate. I believe my error with that was at one point I was dosing too much of the phosphate supplement a day and raised my phosphate too quickly from 0 to 1.1 (hanna checker normal range) in about 2 weeks it looks like. This caused a lot of my coral to die during that period. Prior to this a lot of the coral was doing well and growing SPS, LPS and zoas. The problem I was trying to correct was the rampant cyano outbreak.

As my tank stands now everything is stable. I have a few acropora colonies growing, euphylia are doing great, as are zoas. I struggle to keep and montipora or seriatopora though. My theory is they don't like the higher nitrate. Nitrate is still at about 85. I had an ICP test done and it showed 70 nitrate and very trace phosphate at 0.02. The ATI test actually recommended adding phoshorus.

Now the nitrate level isn't panicking me. However, I would much rather get it down to a more reasonable level of 5-10ppm. Also having a detectable amount of phosphate in the tank would also be a good thing my target would be about .05. My thought process is if I were to dose phosphate properly to reach that level that would balance the system out and the Redfield ratio I have learned a bit about would bring the nitrates down. My concern is the bad experience I had with a lot of coral die off last time I tried dosing phosphate.

So is my fear unwarranted with attempting to dose phosphate again? The lack of phosphate in the tank is quite confusing to me. I have what I would consider a medium bioload of about 15 fish and I feed them 4-5 times a week.

Has the nitrate level been 80 ppm for 1.5 years?

Has the phosphate level been around 0.03 for 1.5 years?

Are you diluting the sample before testing the nitrate level?

 

[Euphyllia97]

In my opinion it makes sense that carbon dosing is not reducing nitrates if theremis no Po4 present. You need both to make it work

 

[Ciwyn]

Has the nitrate level been 80 ppm for 1.5 years?

Has the phosphate level been around 0.03 for 1.5 years?

Are you diluting the sample before testing the nitrate level?

Yes the nitrate has been pretty consistently that level ever since the cycle completed. PO4 was present initially after the cycle, then quickly dropped to zero until I tried dosing phosphate. When I tried the phosphate dosing though I had lot of coral die and most of them not look happy.

I do not dilute the sample at all. The 80ppm number for nitrate was from an ICP test. All my eyeball can tell when using a salifert or nyos test is the nitrate is somewhere between 50-100.

 

[Ciwyn]

In my opinion it makes sense that carbon dosing is not reducing nitrates if theremis no Po4 present. You need both to make it work

I have considered that. I would think if I could get PO4 present the nitrates would lower anyway and carbon dosing may not even be necessary. I am just very hesitant to try dosing phosphate again after what happened last time.

This is not my first tank and I've been in the hobby for about 6 years now. So at this phase I think I understand things, then learn I actually have no idea what I'm doing! lol One lesson that seems to repeat itself is don't mess with things when they are working. The only problem is there are some montipora and birdsnest corals I would love to keep in my tank and I think the high nitrate may be the culprit with those particular corals (then again it may not be).

 

[Dan_P]

Yes the nitrate has been pretty consistently that level ever since the cycle completed. PO4 was present initially after the cycle, then quickly dropped to zero until I tried dosing phosphate. When I tried the phosphate dosing though I had lot of coral die and most of them not look happy.

I do not dilute the sample at all. The 80ppm number for nitrate was from an ICP test. All my eyeball can tell when using a salifert or nyos test is the nitrate is somewhere between 50-100.

OK thanks.

A couple thoughts.

Carbon dosing rates ramp up too slowly to have an impact. You might have stopped too soon increasing the dose. Alternatively, very low phosphate can prevent nitrate reduction during carbon dosing. You might want to reconsider carbon dosing as a nitrate reduction method while dosing PO4.

Whatever you try in your quest to lower nitrate, dilute your sample with RODI water for the nitrate test to get the color where you can actually see a difference in intensity. If you don’t, you might miss the beginning of a success story and quit the approach.

I wonder if the coral death is related to increasing the phosphate level. We need some experts to reconsider your hypothesis.

 

[Ciwyn]

I wonder if the coral death is related to increasing the phosphate level. We need some experts to reconsider your hypothesis.

That's why I started this thread. I would like to hear more about it. Perhaps understand it a bit better. The biggest thing for me is those events coincided with each other and it hit a lot of my coral.

 

[Ciwyn]

So I'm going to post an update from over six months later. I went ahead with phosphate dosing. I started several months ago and got measurable phosphate. What eventually happened was with the dosing my phosphates continued to rise and I would back off the dosing.

Now I haven't done any dosing in about 2-3 months and my phosphate has appeared to stabilize between .05-.1ppm. Basically right where I want it to be. Has anyone else had similar results?

On the negative side this or something else did hurt a bunch of my coral. Another thing I have been struggling with in this tank since the beginning is high nitrate (which recently built a nitrate reactor to hopefully wrangle the nitrate down to less than 20). So I am not sure what has been the biggest stressor to my coral but my guess is that the high nitrates of 80-100 combined with increasing the phosphate from 0 caused a lot of stress on the system. I'm hoping moving forward with these parameters in check I can build a thriving system.