Raising Phosphate without raising Nitrate

[RoaReefer]

Hello everyone! First off - everything is looking great and growing (although a little browning of the SPS). So the current tank is -

20 Gallon
5 Fish (all less than 1" but growing)
25+ pounds of live rock - well cycled
NO Overflow - so no mechanical filtration besides skimming
Skimmer is running a little wet
No Carbon in the system
Kessil AP9x at its highest 55%

4 Gallons a week water change with Nyos Pure salt and RO/DI water

Using Hanna Kits

Nitrate = about 8
Phosphate = 0.00

I feed 3x a day (combo of Vitalis, Nyos True Algea Pellets, Spirulina powder, and Copepod Powder) with the addition of Sea Veggies every day. I also add about a 1/3 teaspoon of frozen lobster and shrimp for the crabs 1x a week.

I REALLY don't want to dose a phos additive like NeoPhos if I don't have to, and I really don't want to feed more.

I have been doing this for 35+ years and looking for suggestions.

Thanks

 

[Justfebreezeit]

I'd dose Phos until you start getting a reading.
The rocks and sand can potentially suck up quite a bit until you finally do. This just means if you choose to just wait until you get it from your current food program that it could take awhile

 

[Randy Holmes-Farley]

dosing phosphate is cheap and easy and far more controlled than the few other ways, such as feeding more and consuming more N.

I recommend food grade sodium phosphate.

 

[mcarroll]

20 Gallon
[....]
Kessil AP9x at its highest 55%

Interesting choice. Like going to the store for milk in a top fuel dragster. (Just in case the answer is interesting...) Reason for not downsizing the fixture?

Nitrate = about 8
Phosphate = 0.00

IMO you are only seeing NO3 building up due to the phosphate shortage that's been created. Phosphate limitation.

Liebig's law of the minimum - Wikipedia

en.wikipedia.org

(Randy has a great piece in the articles section about this.)

4 Gallons a week water change with Nyos Pure salt and RO/DI water

Stop doing water changes until nutrient levels recover. If you must do water changes for some reason, use liquid N and P to raise levels in your water change water to an acceptable range. I'd suggest ≥0.10 ppm for PO4 and ≥ 5 ppm for NO3.

I REALLY don't want to dose a phos additive like NeoPhos if I don't have to,

Why not? It shouldn't be permanent. Think of it like feeding liquid nutrients to your houseplants – no different. (Practically the same thing.) Use the target levels above IMO.

and I really don't want to feed more.

Do your fish approve of this message??!! ;)

It's hard to imagine you couldn't feed more with that many fish, but you would do well to consider scaling down the other demands on N & P first.

Water changes were the only thing you really named so far, and we covered that.

I would consider backing down the air on the skimmer most of the way for the time being as well.

Any other ways the tank is being cleaned or filtered?

 

[RoaReefer]

dosing phosphate is cheap and easy and far more controlled than the few other ways, such as feeding more and consuming more N.

I recommend food grade sodium phosphate.

Thanks!

I guess the solution is dosing or feeding. Phos reading a month ago was 1.02, so quite a swing.

dosing phosphate is cheap and easy and far more controlled than the few other ways, such as feeding more and consuming more N.

I recommend food grade sodium phosphate.

Interesting choice. Like going to the store for milk in a top fuel dragster. (Just in case the answer is interesting...) Reason for not downsizing the fixture?


IMO you are only seeing NO3 building up due to the phosphate shortage that's been created. Phosphate limitation.

Liebig's law of the minimum - Wikipedia

en.wikipedia.org

(Randy has a great piece in the articles section about this.)


Stop doing water changes until nutrient levels recover. If you must do water changes for some reason, use liquid N and P to raise levels in your water change water to an acceptable range. I'd suggest ≥0.10 ppm for PO4 and ≥ 5 ppm for NO3.


Why not? It shouldn't be permanent. Think of it like feeding liquid nutrients to your houseplants – no different. (Practically the same thing.) Use the target levels above IMO.


Do your fish approve of this message??!! ;)

It's hard to imagine you couldn't feed more with that many fish, but you would do well to consider scaling down the other demands on N & P first.

Water changes were the only thing you really named so far, and we covered that.

I would consider backing down the air on the skimmer most of the way for the time being as well.

Any other ways the tank is being cleaned or filtered?

No - no other ways the tank is being filtered or cleaned - as why I was doing water changes. It is 100% skimmer based. I have backed down the skimmer already. 1/2 flow and lowered air intake.

 

[mcarroll]

Thanks!

I guess the solution is dosing or feeding. Phos reading a month ago was 1.02, so quite a swing.

Unless I missed the explanation for that swing, a swing like that would make me think about re-testing and doing a sanity test (on the test kit) using another sample, like tap water or a phosphate calibration standard....maybe not in that order. ;)

Do you know why it went all the way to zero? Seems like it would be A LOT of water changes to take that to zero in a month.

Maybe the 1.02 reading was "off"?

 

[RoaReefer]

Unless I missed the explanation for that swing, a swing like that would make me think about re-testing and doing a sanity test (on the test kit) using another sample, like tap water or a phosphate calibration standard....maybe not in that order. ;)

Do you know why it went all the way to zero? Seems like it would be A LOT of water changes to take that to zero in a month.

Maybe the 1.02 reading was "off"?

Could have been "off" for sure.

Testing has gone from 1.02 to .34 - two weeks later - to zero today. I have only done water changes at 4 gallons every week. Nitrates have gone from 35 -> 25 -> 12 -> 8 over the past few weeks. I have done re-testing - with the same results every time. Not my first rodeo. Salinity is pegged at 35 ppm. I basically have no evap and solid temp.