Does fresh mixed SW degrade over time?

[stunreefer]

I recall reading somewhere that you don't want to leave fresh mixed saltwater sitting for extended periods of time as the calcium will precipitate out, or something along those lines. Generally I mix all my SW, let sit for 24-48 hours prior to use, and refill my container with RO/DI and let sit until I need more SW. I am curious if there would be an issue mixing the salt in with the RO/DI, keeping it heated ~72° F, and airated with a power head, for say, week(s) at a time. What are the negative issues to expect from this?

I use RO/DI with an effluent TDS of 0-1 PPM, and I mix all my water in potable water (food grade) containers, cleaning them out thoroughly every other time (ish) I use them with water and vinegar.

 

[Randy Holmes-Farley]

What brand?

With a mix like Instant Ocean which contains no organics (no vitamins, etc), there is no drawback to letting it sit. Any precipitation happens on first mixing, and there can be a lot of that, but not later once mixed and aerated. Once dissolved, it can sit forever.

 

[stunreefer]

Awesome, thanks Randy.

I use Instant Ocean, or Reef Crystals if it's "on sale" .

Out of curiosity, what brands couldn't you do this with?

 

[Randy Holmes-Farley]

There are vitamins or other organics in Reef Crystals, hW Marinemix Plus BioElements, tropic marin Bio-Actif, Kent, Coralife, and Nutri-SeaWater.

 

[stunreefer]

Thanks.

So no go for RC... looks like I'll stick with IO unless I'm using it quickly.

 

[Uncle Salty 05]

If the mixture sits for extended periods you will need to keep it tightly covered to prevent contamination from dust etc. and to keep evaporation to a minimum.

 

[stunreefer]

The containers I use have a lid on them, and there is just enough room for a power cord (from pump, heater) to fit through. I always double check salinity prior to using, which covers the evporation issue, and due to the size of the opening (for power cord) little to no dust could make it in.

 

[Randy Holmes-Farley]

I sotere mine in closed Brute cans with cut outs for tubing and cords too.

 

[ChuckG]

Randy.. I read someones experiences where they said ALK will deplete over time if continuous flow is applied. Not sure what chemical action is applied by simlple flow but is this not the case?

I have yet to test this..

 

[Randy Holmes-Farley]

I do not think that there will be appreciable precipitation once mixed to normal salinity if the pH is brought to 8.3 or lower by aeration and mixing should not accelerate it. The ocean water stirs for a long time without precipitation.

If you add anything to it, like buffers, that's another story.

That does happen with stirred limewater. That drives in CO2 which causes precipitation of calcium carbonate. Might that be what you heard?

 

[ChuckG]

Not to throw anyone under the bus..

http://reefcentral.com/forums/showpost.php?p=16653168&postcount=21

But the above post is where I read the idea. Which I liked because the thought of being able to more closely match alk and calcium parameters with makeup water sounded like a good idea. Especially since I am already going to the effort to split up my two part dosing into 24 intervals per day.

If I can't effectively drop the alk level of instant ocean by letting it mix in a container for some amount of time then I'm looking at buying more expensive salt that mixes up closer to my desired targets which are much closer to natural sea water.

I trust your experience.. but I am drawn to the challenge for the sake of not spending $80 on salt buckets so I must run a rudimentary test to know for sure. :thumbsup:

So I just mixed 5-6 gallons of Instant Ocean up to 52.5mS/cm @79 degrees. It is in an old 200G salt bucket with a heater and a running maxi jet 1200 to keep it stirred.

Two hours after being mixed with RO/DI the parameters I measured with fresh Salifert kits and my Hannah PH meter are:

Temp 79
PH 8.11
Calcium 420ppm
Alk 14.4 dkh
Magnesium 1440ppm

I will top off the bucket nightly with RO/DI to maintain the salinity and then re measure in 5 days (Sunday).

BTW this bucket of Instant Ocean mixed up at much higher levels of calcium and lower levels of alk when i first opened it. Like I've seen you mention before these buckets must really need to be stirred up dry before mixing.. I have tested this alk kit against the provided reference sample and it is spot on.. at least at 7.3 dkh.

 

[Randy Holmes-Farley]

FWIW, I do not agree with that linked comment that parameters will decline due to stirring.

 

[ChuckG]

FWIW, I do not agree with that linked comment that parameters will decline due to stirring.

yes.. I am with you. Maybe he noted a drop in alk due to bacterial action on ammonia or vitaminsi in either the salt or source water he mixed??

I have seen my new tank's alk drop to 7dkh which after reading your articles I attributed to bacterial action during the initial cycle. There was nothing else in the tank to deplete alk.. Materials like dry limestone rock can not suck alk back out of the water can it?

 

[cham]

I make up a months worth of water change's each month with reef crystals. Allowing the water to sit for up to a month (with a power head moving it the entire time) is an issue?

 

[rkb]

I make up a months worth of water change's each month with reef crystals. Allowing the water to sit for up to a month (with a power head moving it the entire time) is an issue?

This is very close to what I do- I mix up about 40g in a Brute which is roughly 5 weeks worth of water changes. The salt mix is Reef Crystals and the Brute container has a 200w heater and 350gph powerhead for circulation.

 

[Randy Holmes-Farley]

Allowing the water to sit for up to a month (with a power head moving it the entire time) is an issue?

You may not have the same vitamins in it at 1 month as when fresh mixed. Is that a concern? I do not know. I’ve not seen any info suggesting the vitamins are useful, nor what they may become over time 9nnotr even how much of what is added in the first place).

I suspect it doesn't matter, as long as you stir it. I would not leave it unstirred as I would Instant Ocean.

 

[Randy Holmes-Farley]

Materials like dry limestone rock can not suck alk back out of the water can it?


Dry limestone can briefly suck up a tiny but, but it is not an ogoing process.

 

[ChuckG]

Retested this evening. Probably not enough control being applied here to discern one way or another yet. The values did drop.. but I have no idea if they settled to tonight measurements 12 hours after the initial mixing or if the values have been steadily dropping all along. I will have to let the same bucket go another week then re test.. maybe perform a couple test in between.

I think it is possible that I did not wait quite ling enough to run my initial testing and the values measured tonight have been the same all week. Tonights values are very close to the values listed in the "Synthetic Salt Mixes" sticky thread.

Sticky thread Measurements

Instant Ocean (new) 400 calc 11dkh alk 1350 mag

My measurements tonight

Instant Ocean (new) 380 calc 11.5dkh alk 1365 mag

 

[Randy Holmes-Farley]

That's certainly well within what one would expect, and are fine.