NO3/PO4 ratio fine then not

[Monkeynaut]

I am curious how I ended up with this set of results. I had been seeing NO3 and PO4 drop in my tank at the same rate in a 16 to 1 ratio.
I then noticed that after my cheato was big enough to stop rolling in the sump that it fanned out across the top of the sump and turned white directly under the H380.
The week I saw this with the cheato I took measurements of .11 PO4 (phosphorus checker by hanna) and 0 NO3 (redsea test kit).

Why did my NO3/PO4 ratio get out of wack?

 

[Randy Holmes-Farley]

There's no particular reason to think that nitrate and phosphate will decline in a particular ratio.

Many reef tanks end up with some excess phosphate, probably because there is denitrification taking nitrate out of the picture while not substantially impacting phosphate.

 

[Monkeynaut]

I wonder what might have happened to throw it out of balance like it had been. I am hypothesizing that the algae quit growing when it quit being able to rotate and totally covered the water surface.
I still have 0 nitrate but .07 phosphate today, which is a few days after removing all but a couple softballs of cheato. It freely rotates now with lots of room for growth.

I am very interested to see how low the cheato will drive phosphates if I keep it trimmed to rotating and if it quits growing so quickly if I start getting zero/zero readings.

 

[madweazl]

Mine has never been able to tumble (or move for that matter) with no observable affects (negative or positive).

Block-O-Macro

Perhaps the intensity of the H380 is too much if exposed constantly; have you tried elevating the light to see if there is a difference? Reducing photo-period perhaps?

 

[Monkeynaut]

@madweazl I am unable to raise the light any further in my stand. I am running it for a longer photoperiod (18 hours) to lower nutrients and that had worked until it was unable to move any more.

What light and photoperiod are you using on your refugium and what algae is that other than cheato? What are your nutrient levels?

 

[Monkeynaut]

There's no particular reason to think that nitrate and phosphate will decline in a particular ratio.

Many reef tanks end up with some excess phosphate, probably because there is denitrification taking nitrate out of the picture while not substantially impacting phosphate.

What is supposed to be taking phosphate out of the water column in our reef tanks?

 

[hyprc]

What is supposed to be taking phosphate out of the water column in our reef tanks?

Corals use some. For control, cheato and other macros do a pretty good job.

 

[madweazl]

@madweazl I am unable to raise the light any further in my stand. I am running it for a longer photoperiod (18 hours) to lower nutrients and that had worked until it was unable to move any more.

What light and photoperiod are you using on your refugium and what algae is that other than cheato? What are your nutrient levels?

I have/had a few types of caulerpa (paspaloides, sertulariodes, and prolifera) along with the chaeto (hitchiked its way in on one of those as I hadnt intended on keeping it). Light is a Kessil H80 over a 12.5x13.5.x10 (LxWxH) refugium. Light is mounted 7" above the water on full intensity on the "grow" setting. Photo-period is 16 hours.

Nitrates - <1
Phosphates - <.1

Log history

 

[hatfielj]

In my experience cheato will ultimately drive nutrients too low. I bet the die off you saw was from the lack of nitrate. With your phosphate still high, you could simply dose some nitrates to help get that down. Your macro algae will probably demand a constant supply of nitrates moving forward.

 

[Randy Holmes-Farley]

What is supposed to be taking phosphate out of the water column in our reef tanks?

Any photosynthetic organism likely is, but many folks find they need a boost to phosphate export more than nitrate export, hence the use of methods such as GFO, lanthanum, even nitrate dosing to get balanced methods (like macroalgae) to take up the residual phosphate.

 

[Randy Holmes-Farley]

I wonder what might have happened to throw it out of balance like it had been. I am hypothesizing that the algae quit growing when it quit being able to rotate and totally covered the water surface.
I still have 0 nitrate but .07 phosphate today, which is a few days after removing all but a couple softballs of cheato. It freely rotates now with lots of room for growth.
.

I'm not sure that's a viable explanation for nitrate gone but phosphate remaining.

Unable to grow because nitrate is gone seems more plausible.