Strontium Dosing

[Khazmodain]

I'm trying to find a product to carry out a corrective dose for Strontium. The only product I've found that actually provides guidance regarding how much to dose in order to raise Sr by a specific level is Brightwell. Unfortunately their label just appears to be flat out wrong.

The stock solution guidance is inconsistent with their reference guidance (a difference of about 60%). There's also references to Sr levels of 412 ppm.. which is clearly crazy. Wondering if they took this label from their Potassium product. Anyways, I'm a little hesitant to pull the trigger here.

Although they do provide the ingredient and concentration so I'm sure someone who is more inclined in chemistry could provide the correct dosing guidelines. Trying to figure out how much I would need to dose of a Strontium product to increase Sr from 3.2 to 8.0 in a 400 gallon net volume.

Any thoughts?

Thanks!
Eric

Instructions and Guidelines

Advanced: Create a stock solution by dissolving 2 grams (~1 teaspoon) of Strontion-P in 8-fl. oz. of fresh water (preferably purified); each ml of the solution will increase the strontium concentration ("[Sr2+]") in 1 US-gallon (3.785 L) of water by 0.75 ppm. [Reference: Each g of Strontion-P will increase the [Sr2+] in 1 US-gallon (3.785 L) of water by 143 ppm.] If initial [Sr2+] in aquarium is below 412 ppm, add stock sol'n at maximum rate of 10 ml per 20 US-gallons daily until desired [Sr2+] is attained, then dose daily or weekly as needed (see below). Maintain [Sr2+] within a range of +/-2 ppm. Once desired [Sr2+] has been acquired, measure aquarium's [Sr2+] at the same time each day over a one- to two-week period to determine the daily rate of strontium uptake (i.e. the decrease in strontium). To determine daily dosing rate (preferable to weekly dosing): estimate volume of water in entire aquarium system (US-gal.); divide the daily decrease in [Sr2+] by 0.75; multiply this number by volume of water in system to obtain daily ml of stock sol'n required to maintain stable [Sr2+].



Caution: Keep out of reach of children. Not for human consumption.


Guaranteed Analysis
Strontium (min) 54% (540,000 ppm)

Ingredients
Strontium chloride (anhydrous)​

 

[FishAndPhysics]

Why do you want to dose strontium? Shouldn't water changes replenish it?

IMO, most supplements beyond mag ca and all are of dubious value at best. I suppose at some system size (thousands of gallons) it becomes cheaper to measure all these things properly and dose all of them than to do water changes, but I don't think that applies to most hobbyist tanks.

 

[Khazmodain]

Why do you want to dose strontium? Shouldn't water changes replenish it?

IMO, most supplements beyond mag ca and all are of dubious value at best. I suppose at some system size (thousands of gallons) it becomes cheaper to measure all these things properly and dose all of them than to do water changes, but I don't think that applies to most hobbyist tanks.

Because it's low and water changes aren't keeping up with it. Sr has been down to be important for coral health and growth. Also dosing ca, alk, mg, KNO3, Fe, I, K. Completely agree with a smaller system it can be handled via water changes. The time, effort, and cost of water changes vs dosing elements tips on a smaller system than you're thinking.

 

[FishAndPhysics]

Well then, it's a basic dilution question, assuming you have a way to measure the strontium concentration, and know how much you want to add, AND the manufacturer gives a real concetration (54% strontium makes no sense, strontium chloride is already only about 50% strontium). ESV is generally good about giving real chemistries with real concentrations. Suppose you know the concentration of your supplement is X (in moles/L), the volume of added supplement is Vx (in liters) the starting concentration of your tank is Y, and the volume of your tank is Vy, then the concentration of your tank after dosing will be (Vx*X+Vy*Y)/(Vx+Vy). To make the math clear, the numerator is the total amount of strontium (in Moles) in your dose and your tank when they are separate (volume*concentration for each) and the denominator is the total volume (obviously, Vx is much, much smaller than Vy and irrelevant in the denominator, but it is there for clarity). Once you think you have calculated a dose in ml of chemical/gallon, I'd mix up a gallon of fresh saltwater and dose at the calculated level and make sure it gives you the change you want before you start chucking strontium in your tank.

 

[Khazmodain]

Thank ya much. Is 54% strontium in a dry strontium chloride powder out of line? Or is close to 100% concentration/purity not feasible here?

Unfortunately ESV has even less information on their Sr product.

 

[FishAndPhysics]

Ah, I'm stupid. Yes, strontium chloride powder should be around 50%. Exactly:

Atomic mass Sr = 87 AMU
Atomic mass Cl = 35 AMU
The formula is SrCl2, so the mass is:
87 + 35*2 = 157
So then the percentage Sr by mass is:
87/157 = 55%. The percentage point difference between my calculation and theirs is likely that the SrCl2 is not pure, so there is 1-2% some mystery substance that isn't included in my math.

 

[dkeller_nc]

Actually, there's a problem with that. Strontium chloride exists in an anydrous, a monohydrate and a hexahydrate form with corresponding different molecular weights.

It's not impossible, but somewhat doubtful that either company would be supplying the anhydrous form. For the anhydrous form, your math is correct - it would be approximately 55% Strontium. The monohydrate form would be almost exactly 50% Strontium. The hexahydrate form would have about 33% Strontium in the material.

Your guess is as good as mine about which one they're supplying.

 

[FishAndPhysics]

His copy-pasted bottle description listed anhydrous. Assumed any errors would be be omission, not outright falsehood.

I suggest that we measure few things in this hobby to <5% accuracy (although stability of much less than <5% can be important). So, if you're worried, you're really trying to make sure it isn't the hexahydrate.

I suggest two methods to tell: 1. You can simply dissolve some SrCl2 in water, and measure it with your test kit. 2. The solubility of SrCl2 (anhydrous) is fixed, so in the hydrate forms the mass solubility will appear to be much higher, since the powder will be in large part water. So, put a cup of 10 mL of RODI at 20C on a scale, and keep adding powder until it stops dissolving. Per wikipedia, the solubility at 20C of the anhydrous is 53.8g/100mL. If you can get significantly more than 53.8g to dissolve in your 100 mL of water, leaving a clear solution, it might be hexahydrate. Otherwise, anhydrous. If I were you, do both and see if they agree.

 

[dkeller_nc]

His copy-pasted bottle description listed anhydrous.

Oops, missed that. Personally speaking, I think I'd make up the dosing solution to a known concentration based on the assumed anhydrous form in the bottle, calculate how much to add to the aquarium to get 1/4 of the way to the goal, then do a test on the tank water for Sr concentration right before adding it, add the dose, wait a couple of hours, then test again.

If the material is truly anhydrous, that would yield the absolute maximum of Sr++ added to the tank. If it turns out to be the monohydrate or the hexahydrate, the amount of Sr++ in the tank will be considerably lower, and ideally, one would like to err on the side of slowly raising the concentration of any trace element instead of all at once.

 

[Khazmodain]

Thank you both very much for your input. I had intended to administer corrective doses quarterly to semiannually (depending on Triton ICP results). Might have to buy a Sr kit.. just not sure how much I trust a hobby level Sr kit... haven't seen the best reviews.

 

[FishAndPhysics]

If you're getting chemistry done professionally, you should be able to know, at least at one value, how accurate your test kit is. Precision you can determine by simply running the test kit on the same sample a bunch of times. Should inform your confidence level in your test kit.