Approach to Nutrient Dosing

[Fish_Fry]

I'm going to start dosing nutrients for the first time and I'd appreciate some feedback on my approach.

Background:
Tank is a lightly stocked 75 gallon, with 4 small fish, handful of frags and some macro algae in the display and sump. Tank has been cycled for about 5 months. I'll be slowly increasing the livestock over the next few months. I've started cultivating phyto and pods with the intention of someday having a dragonette.

Nitrates & Phosphates were trending lower and they have been zero for about a month. I've done all the basic things to increase them:

Feeding - I was feeding a mix of frozen and dry 2x a day. I've increased the portion size and now I feed 2 - 4x a day.

Filter Sock Swap - Instead of replacing every 3 days I wait until it starts overflowing and making noise

Water change - I was changing 20-25% every 2 weeks, I'm now waiting 3 weeks.

Refugium Photoperiod - I lowered from 12 to 6 hours. Interestingly my Aqueon Clip on light just failed so the photoperiod has been zero for about 5 days. I'm planning to set up a different light this weekend, while it gets replaced under warranty.

Since the typical ways to increase nutrients haven't worked I've decided to dose nitrate and phosphate.

Dosing Approach:
I have purchased food grade Sodium Nitrate and Trisodium Phosphate. I have a link to the calculations on how much to add, but this is where I can use some suggestions.

I'm planning to dose, wait 30-60 minutes and test. Does it make sense to make a 1/2 strength solution and dose 2x as much so there is a wider margin of error? How much per day should I raise my levels? Once I find my equilibrium with regards to dosing and consumption, how infrequently can I dose? Would 2x a week work? I'd prefer to not set up a dosing pump until I know what the final bioload is going to be. I occasionally travel for work so I'd like not have to dose everyday, since it would be one less thing for my wife to have to manage while I'm gone.

I'm envisioning using a squirt bottle and a small measuring cup. Once I determine the ratio of NO to PO can I combine them into one solution? Meaning if my tank needs 10 ml of Nitrate and 5 ml of phosphate, can I make a 2:1 solution and dose 15 ml? I don't think they will precipitate but I want to ask. I recognize that overtime the consumption of one might change, but I'm envisioning having enough combined solution to last a month or two.

Thanks

 

[Timfish]

I wouldn't dose nitrate. Of the various organic and inorganic forms nitrate is corals least favorite form. Urea and ammonia from fish on the other hand is their prefered forms. I'd add more fish and feed the fish more.

 

[Fish_Fry]

I'm definitely going to add more fish. I expect it will take a little while while I figure out what I want, source & QT them.

I recognize that ammonia is the preferred source, but it seems risky to dose it. I thought NO3 was all the same regardless of source.

 

[Randy Holmes-Farley]

I thought NO3 was all the same regardless of source.

It is. Once nitrate is in the water, nothing that uses it can know where it came from.

What are your current nitrate and phosphate values?

I suspect it may take a long time to get to a stable ratio becuase once phosphate is very low, a lot of what you dose is going to bind to rock and sand, then over time that peters out and you might be able to dose a mixture.

 

[Fish_Fry]

I suspect it may take a long time to get to a stable ratio becuase once phosphate is very low, a lot of what you dose is going to bind to rock and sand

That explains what happened yesterday. Both were at zero. I dosed Nitrate to get to 4 ppm & it worked. However, I separately dosed phosphate that should have taken me to 0.03 and yet my level remained at zero.

I thought I made a mistake somewhere, but it must be the rock & aragonite sand binding it.

Should I continue to dose cautiously, knowing it stay zero until one point it doesn't?

I don't like the idea of chasing numbers but I'm worried about being at zero while I'm waiting for the tank to become more heavily stocked.

Thank you very much.

 

[Lavey29]

I have basically the same size tank and somewhere around the 5 month mark I had to dose neophos and neonitro. I double dosed for multiple weeks to get measurable numbers. After some months the tank balanced and dosing was not needed. I run a fuge too.

 

[Randy Holmes-Farley]

That explains what happened yesterday. Both were at zero. I dosed Nitrate to get to 4 ppm & it worked. However, I separately dosed phosphate that should have taken me to 0.03 and yet my level remained at zero.

I thought I made a mistake somewhere, but it must be the rock & aragonite sand binding it.

Should I continue to dose cautiously, knowing it stay zero until one point it doesn't?

I don't like the idea of chasing numbers but I'm worried about being at zero while I'm waiting for the tank to become more heavily stocked.

Thank you very much.

Yes, keep dosing the phosphate and maybe up the dose.

 

[Lavey29]

That explains what happened yesterday. Both were at zero. I dosed Nitrate to get to 4 ppm & it worked. However, I separately dosed phosphate that should have taken me to 0.03 and yet my level remained at zero.

I thought I made a mistake somewhere, but it must be the rock & aragonite sand binding it.

Should I continue to dose cautiously, knowing it stay zero until one point it doesn't?

I don't like the idea of chasing numbers but I'm worried about being at zero while I'm waiting for the tank to become more heavily stocked.

Thank you very much.

I discovered the same which is why I had to double dose to get measurable numbers.

 

[94Rudolph]

Yes, keep dosing the phosphate and maybe up the dose.

Would adding urea（CH4N2O/CO(NH2)2）be better than sodium nitrate?

 

[Randy Holmes-Farley]

Would adding urea（CH4N2O/CO(NH2)2）be better than sodium nitrate?

I do not know, but you cannot monitor the urea concentration, so I wouldn't dose it except purely as an experiment.

 

[94Rudolph]

I do not know, but you cannot monitor the urea concentration, so I wouldn't dose it except purely as an experiment.

I'll watch the algae grow. The added nutrients become unmeasurable as they enter the energy cycle. Sometimes observing biological states is better than absolute measurements.