Stable parameters, low phosphates...

[ReefnBeans]

Okay y'all, looking for some thoughts on phosphate management.

My tank has been running for about 4 months now and overall things seem to be heading in the right direction. Corals are opening, alk consumption has started, and the tank feels like it's finally maturing.

My question is phosphate. It's consistently testing between 0.00-0.01 ppm. I was able to get it up to 0.03 ppm, but the very next day it was back down to 0.01 ppm.

Current parameters:

• Alk: 8.1 dKH
• Nitrate: 14.2 ppm
• Phosphate: 0.01 ppm
• Salinity: 1.025-1.026

Livestock:

• 2 clownfish
• Yellow watchman goby
• 2 mushrooms
• Torch
• Hammer
• Recovering octospawn
• 5 zoa frags
• Duncan

Feeding:

• Pellets 2x/day
• Rotating mysis feedings
• No refugium
• No phosphate-removing media

The corals generally look healthy, but I'm wondering if I should just let the tank continue to mature naturally or if I should be trying to keep phosphate closer to 0.03-0.05 ppm.

For those who have been through this stage of a young reef, would you stay the course or make adjustments?

 

[mcarroll]

If you can do anything to downscale filtration to a baseline of just live rock and a protein skimmer, do it. That includes skipping regular water changes if needed.

IMO your corals are all good feeders, relatively speaking, so IMO they aren't going to be as sensitive to low dissolved nutrients as some corals. Keep up the feeding routine (your fish feed the corals) but don't overdo it.

 

[ReefnBeans]

If you can do anything to downscale filtration to a baseline of just live rock and a protein skimmer, do it. That includes skipping regular water changes if needed.

IMO your corals are all good feeders, relatively speaking, so IMO they aren't going to be as sensitive to low dissolved nutrients as some corals. Keep up the feeding routine (your fish feed the corals) but don't overdo it.

One thing I'm trying to better understand: at what point should I actually be concerned about corals becoming phosphate limited?


I've read that corals can begin consuming internal phosphorus reserves when phosphate drops below ~0.02 ppm, but I'm not sure how much weight to put on that number versus overall coral health and nutrient availability.


For example, if I'm consistently testing 0.01 ppm phosphate but nitrates are around 14 ppm, corals are extended, and alk is being consumed, is that still considered a phosphate-starved system? Or is 0.01 simply reflecting that phosphate is being utilized quickly rather than absent?


Curious how you distinguish between "low phosphate" and "problematically low phosphate."

 

[slingfox]

I assume you started with dry rock and bagged sand? If so you are likely going through the phase where the rock and sand are absorbing phosphates. Eventually that process will end and you will start seeing phosphates in the water column. Eventually you may need to deal with too high phosphates!

For now I would just feed your normal amount and reduce filtration and skimming until phosphates are detectable. This can take a half year or year or more. There is potential Dino’s will come which will be annoying. You could dose phosphates to speed up the equilibrium process. You could also add more fish so you can feed more.

 

[ReefnBeans]

Thanks for that info!

 

[Randy Holmes-Farley]

I'd personally feed more or dose phosphate.

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

• 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.

 

[mcarroll]

One thing I'm trying to better understand: at what point should I actually be concerned about corals becoming phosphate limited?


I've read that corals can begin consuming internal phosphorus reserves when phosphate drops below ~0.02 ppm, but I'm not sure how much weight to put on that number versus overall coral health and nutrient availability.

The insufficiency of food items places more weight on dissolved phosphates (and N, etc)as compared with what corals might be likely to encounter in the wild.

For example, if I'm consistently testing 0.01 ppm phosphate but nitrates are around 14 ppm, corals are extended, and alk is being consumed, is that still considered a phosphate-starved system? Or is 0.01 simply reflecting that phosphate is being utilized quickly rather than absent?


Curious how you distinguish between "low phosphate" and "problematically low phosphate."

Corals tend toward bleaching and tissue loss when phosphates are truly "missing".

Thing is, it takes time for symptoms like those to show up for the reasons you outlined (eg using up reserves) and others. So being reactive to low nutrient levels is often not productive....sometimes when symptoms show up it's already too late.

So, somewhere in the literature I bumped into 0.03 ppm as a minimum required for photosynthesis. Somewhat that's an arbitrary value to pick since keeping 0.03 in the water doesn't really guarantee the coral access to 0.03 ppm....but it's a start.

To allow for the other factors that affect availability, targeting 0.05 ppm for PO4 is a simple way to keep a margin of safety.

This article talks and shows more about how phosphate deficiency can impact a coral:

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Article Link: Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates Authors: Rosset, S., et al. Journal: Marine Pollution Bulletin (2017)…

reefsuccess.com

 

[ReefnBeans]

The insufficiency of food items places more weight on dissolved phosphates (and N, etc)as compared with what corals might be likely to encounter in the wild.


Corals tend toward bleaching and tissue loss when phosphates are truly "missing".

Thing is, it takes time for symptoms like those to show up for the reasons you outlined (eg using up reserves) and others. So being reactive to low nutrient levels is often not productive....sometimes when symptoms show up it's already too late.

So, somewhere in the literature I bumped into 0.03 ppm as a minimum required for photosynthesis. Somewhat that's an arbitrary value to pick since keeping 0.03 in the water doesn't really guarantee the coral access to 0.03 ppm....but it's a start.

To allow for the other factors that affect availability, targeting 0.05 ppm for PO4 is a simple way to keep a margin of safety.

This article talks and shows more about how phosphate deficiency can impact a coral:

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Article Link: Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates Authors: Rosset, S., et al. Journal: Marine Pollution Bulletin (2017)…

reefsuccess.com

This is great. Thank you for taking the time to reply.

Given how young my tank is do you think it's just the sand and rock soaking up phosphate giving that consistent that my phosphates are hovering around. 01? Do you think it's just a matter of maturing more and seeing how the corals settle in before I start worrying about the tank being truly phosphate limiting?

 

[mcarroll]

This is great. Thank you for taking the time to reply.

Given how young my tank is do you think it's just the sand and rock soaking up phosphate giving that consistent that my phosphates are hovering around. 01? Do you think it's just a matter of maturing more and seeing how the corals settle in before I start worrying about the tank being truly phosphate limiting?

I took the point of view of your corals, giving them priority over what's "good". From that point of view, I don't care what the cause of 0.01 is.

I don't even know numbers, I'm a coral!

All I know is that at 0.01 I don't have access to "enough". But if I can get enough food, I don't care.

That's a big "if" in an aquarium.

If I consider frags vs colonies, then consider that frags tend to be MUCH more adaptable than larger frags or colonies. As your corals grow, their adaptability shrinks and their demands grow.....the price of success, if you will.

A lot of tanks go through problems around the 1-2 year mark at least in part because of these coral changes.

So, IMO work on letting nutrient levels increase naturally as much as possible. Feed the fish well, but don't overfeed (ie waste food).

Lastly, 0.01 is within the error rate of testing, so may actually be 0.00. IMO you really want to hedge on the side of "enough" rather than "too little".

 

[Gsponi]

Just ATI P.

i need to dose Po4 and its easy .
I prefer to dose than to absorbe.

 

[ReefnBeans]

I took the point of view of your corals, giving them priority over what's "good". From that point of view, I don't care what the cause of 0.01 is.

I don't even know numbers, I'm a coral!

All I know is that at 0.01 I don't have access to "enough". But if I can get enough food, I don't care.

That's a big "if" in an aquarium.

If I consider frags vs colonies, then consider that frags tend to be MUCH more adaptable than larger frags or colonies. As your corals grow, their adaptability shrinks and their demands grow.....the price of success, if you will.

A lot of tanks go through problems around the 1-2 year mark at least in part because of these coral changes.

So, IMO work on letting nutrient levels increase naturally as much as possible. Feed the fish well, but don't overfeed (ie waste food).

Lastly, 0.01 is within the error rate of testing, so may actually be 0.00. IMO you really want to hedge on the side of "enough" rather than "too little".

Awesome thanks for the advice