What is an acceptable amount of excessive Sodium imbalance?

[JunglePete]

I want to add microalgae directly to an aquarium system. The microalgae will be fertilized with a modified F/2 formula that contains NaNO3 and NaH2PO4·H2O as the 2 main macro nutrient ingredients as well as significant amounts of Na2EDTA·H2O.

The NO3 and PO4 can be sequestered and exported via the microalgae and other pathways, but my main concern is the accumulation of sodium (Na) over time.

I calculate that with 10% monthly water changes (0.333% per day) the Na concentrations will creep up to and level off at about 2.57% above normal levels. (From 10,800ppm to 11,078ppm Na).

My question are

1) just how high of an imbalance of Na relative to other ions in the aquarium water is acceptable?

2) What are the repercussions of such an imbalance? I assume similar, raised Na, situations have occurred with significant additions of Baking soda (sodium bicarbonate) added over time.

3) Are there other solutions to this problem (other than larger water changes)?

Also want to note that the addition of Chloride via the algae fertilizer seems insignificant… 24 to 2284 (24 moles Chloride to 2284 moles Sodium).

I hope this question makes sense and thank you in advances for any advice.

 

[Randy Holmes-Farley]

How did you determine that number?

Assuming it is correct (I might have expected an even smaller number), I do not consider it any issue. It is well within the range seen by reefers.

Folks dosing sodium bicarbonate or sodium carbonate are likely adding far more than you.

 

[JunglePete]

I appreciate your response. I'll type up my calculations and post shortly.

 

[JunglePete]

The “normal” F/2 solution for growing micro algae has 882 µMols nitrogen, but is generally lacking in nitrogen (and PO4) so I am considering upping the amount to as much as 2000 µMols NO3, common in some other mediums.

Ingredients (per L) for major nutrients:

2002 µMols NaNO3
82.2 µMols NaH2PO4 · H2O
100 µMols Na2EDTA · 2H2O

2002 µMols Na
82.2 µMols Na
200 µMols Na

2284 µMols "excess" Na per L in Algae Solution

Plan:
200L of algae (with above ingredients) will be added to 11,356L (3000 gallon) system every day.
(The 200L algae volume added, overflows out of the other end of system and is reused to make more microalgae solution... the 200L, essentially recycled, staying in the system)

Math:

Moles of Excess Na in the Algae Solution:

2284 µmols = 0.002284 moles of excess Na in a Liter

0.002284 moles x 200L = 0.45682 moles of excess Na in the 200L algae addition

So… 0.45682 excess moles of Na added to the system daily.


Water Change and maximum Excess Na levels

10% monthly water change (0.333% per day)

10 gallons of the 3000 gallon system will be changed out daily with new salt water.

10/3000 = 0.003333…

Amount added daily to system / Amount removed from system daily = the maximum amount that can accumulate in system so…

0.45682 moles / 0.003333 = 137 moles

So, 137moles excess Na is that maximum amount of excess Na moles that can accumulate in system.


Maximum amount of excess Na in this system (based on algae addition)

Natural sea water has 0.4697899 moles Na per Liter.

11,356L system x 0.4697899 moles Na per Liter = 5,335 moles of Na normally in System

5,335 moles of Na normally in System + 137 moles excess = 5472 moles of Na

Moles Na in System with excess / Moles Na normal = amount of excess
5472 / 5335 = 102.57% = 2.57% extra Na

 

[JunglePete]

With 137 moles of excess Na in the system , at 22.989gms per mole, thats around 3 kg of sodium floating around. That got me thinking that the elements in salts tend to always have an oppositely charged partner. And I wondered if there is an understanding of what happens to this 3kg of sodium Na+ floating around in the system with out a Cl- (or other (-) element) partner.

 

[Randy Holmes-Farley]

Let's look at it differently.

So… 0.45682 excess moles of Na added to the system daily.

That is 10 grams per day in 11,340 L

Thus you are adding each day 10,000 mg/11,340 L = 0.9 mg/l = 0.9 ppm per day.

In a year, without any water changes, you will go form 10,500 to 10,828 ppm.

Water changes will drop that lower, so I see no issue at all.

 

[JunglePete]

Wow! Six clear, concise lines of explanation, that takes me over 30 lines to explain.
Your a wonderful man Randy Holmes-Farley!
I really appreciate your help and all your great articles. They've helped me immensely.
Thank you

 

[Randy Holmes-Farley]

lol

You're welcome and thanks!

Happy Reefing.