Reducing nitrates

[Ilya_Tihomirov]

HOW?
Reduce nitrates without reducing phosphate? The situation is as follows: nitrate is 25-50, phosphate is 0.05-0.1, and when carbon is dosed, the phosphate drops to 0 immediately, while nitrate decreases very little. The system contains live rock. APR is dosed. The system is 7 months old.

 

[RisqEM]

Aside from carbon dosing, I usually add some beneficial bacteria like Microbacter 7 a little before or after the carbon dosing. Also I do small water changes weekly, 10% and that helps keep everything in line.

The carbon dosing usually takes a little while for the effects to show up. How long have you been doing it? And one last addendum, although that number is high, if the corals have been happy for a long time, it might be ok and they’re used to it.

 

[Dan_P]

HOW?
Reduce nitrates without reducing phosphate? The situation is as follows: nitrate is 25-50, phosphate is 0.05-0.1, and when carbon is dosed, the phosphate drops to 0 immediately, while nitrate decreases very little. The system contains live rock. APR is dosed. The system is 7 months old.

You will need to dose phosphate. The biological process that consumes nitrate also consumes phosphate.

 

[Ilya_Tihomirov]

You will need to dose phosphate. The biological process that consumes nitrate also consumes phosphate.

If you don't add carbon, phosphate stays at 0.1, while nitrate gradually increases. Corals are doing well, but many acroporas are starting to take on a predominantly green color. (ICP is fine, iron is normal, and all other parameters are ideal—only rubidium is a bit low.)
When you start dosing carbon, phosphate immediately drops to 0, while nitrate only slowly drops slightly. Water changes have a short-term effect, and nitrate returns to its normal levels. Dosing phosphate risks the risk of having to deal with high phosphate levels later.

 

[rishma]

When you start dosing carbon, phosphate immediately drops to 0, while nitrate only slowly drops slightly.

This is the opposite of what most people observe. Carbon dosing tends to be more effective at reducing nitrate with a smaller effect on phosphate.

Dosing phosphate risks the risk of having to deal with high phosphate levels later.

I dose phosphate daily and have for years. Many people do. If dosed and monitored, I don’t think this is a significant risk.

 

[DiscoStuart]

My tank went through the full roller coaster and seems to finally be stabilizing 6-7 months in.

Initially, my dry rock was massively absorbing phosphate, and so readings were always at zero, and I had to dose to avoid (and recover from) dinos. Eventually, the rock soaked up as much as it seems that it could.

I then had a problem with phosphates creeping up and also very high nitrates (in part due to avoiding water changes while fighting dinos, in part due to my mastertronic failing while away on holiday and over dosing nitrates when trying to recover from nutrients bottoming out). So I ended up dosing NoPox. As another commenter had mentioned, it's much more effective on nitrates than phosphates. Once I got nitrates under control I started using a tiny bit of RowaPhos to slowly try and get my phosphates from 0.2 down to 0.1. That's going slowly but I'm okay with it. So a bit of a journey but slow is the name of the game.

I'm hopeful I can find stability without dosing, but we'll see!

 

[Ilya_Tihomirov]

Carbon dosing tends to be more effective at reducing nitrate with a smaller effect on phosphate.

It's strange, but in all my aquariums (this is my fourth), I've noticed an accelerated phosphate decline when I dose carbon. Nitrate has always been slower. I was advised to install an algae filter.

 

[Fish Fan]

Like @rishma said above, carbon dosing shouldn't cause your phosphate to drop to zero, it affect nitrate much more than phosphate.

That said, your numbers are 100% fine, in my opinion. I like to follow the guidelines from Randy Holmes-Farley found here:
https://www.reef2reef.com/ams/randy’s-thoughts-on-nutrient-target-ranges.1087/
From the above:

• Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
• Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
• Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
• Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
• Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
• Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.

I hope this helps!

 

[Randy Holmes-Farley Verified Community Expert]

It's strange, but in all my aquariums (this is my fourth), I've noticed an accelerated phosphate decline when I dose carbon. Nitrate has always been slower. I was advised to install an algae filter.

Growing macroalgae for nutrient export is a fine plan, IMO. It's my primary export.