Long Term Saltwater Storage Without Dropping DKH... Possible??

[kurt_n]

Interesting thread. Been storing 20g of 80ish degree Reef Crystals made up to 1.025 for months on end for 8+ years. I *try* to keep my tub full, but total quantity stored will be between 10 and 20 gallons at any time. When it gets a little low I add more saltwater in 3.5g increments. I have a powerhead in the covered tub to keep the water moving and aereated, as well as the heater.

About every 6 months, I empty the tub and clean it and fill it back up again. There's definitely a brownish calcium buildup that coats the bottom and bit of the sides of the container, but in all the years of doing this I've *never* noticed a measurable drop in calcium or alkalinity. And I definitely keep tabs on it.

 

[blueramSeattle]

The precipitation is a pH thing. If you are dosing ALk (but not a calcium reactor) you can just drop the pH in the storage tank to get everything back into solution. Just beware that it will crash out when you bring the pH up or you will have to monitor the pH in your system.

If you have a film at the bottom of your mixing container I would leave it or clean out when it gets nasty. By having solids in contact with the solution you are guarenteed to be saturated. Anything that falls out durring mixing will call out anyways (abiotic calcium deposition) or get used by your stony animals and need to be replaced anyways.

The only time I would be worried would be if your water has phosphate, copper, or heavy metals. I seem to recall (to lazy to look it up) that the Ca crystallization will take other things with it. This was given to me as the reason that reusing sand from the "recycled" bin at the fish store is dangerous as a drop in pH or uptake can start dissolving the sand and releasing crud. Could just be an upsell tactic though.

 

[MarlinHooker]

I'm in the middle of setting up a Genesis auto water change system and was planning on chnaging out 2 gals every 12 hrs, 24/7. My seawater storage bin is 70 gals so I was only going to make seawater once a month. I use Red Sea Coral Pro now but only make up 20 gals the night before PWCs and only mix the salt for 2-3 hrs.

Guess I'll need to run some tests to see if the Alk significantly drops over a month. I do run a Ca Rx so I don't know if that makes a difference here ...

 

[Napoleon I]

I have two 55 gallon barrels. One salt, one fresh RO/DI water. I have an air stone in each. I have never even checked the Dkh of my stored salt water but my tanks hardness stays a solid 7.8 with the dosing of soda ash I am using. Maybe it is because I run my hardness lower than some that I have not noticed any swings when doing water changes. If anything my hardness tends to rise a little after a WC. I use Reef crystals FWIW.

Jeff

 

[zakdigital]

Hey Guys, joined for this quality thread!

Any new discoveries in the last few months?

I am experiencing this storage issue as well. 20g brute w/ ro + hw marinemix -> 3x5 gallon sealed jugs stored in the garage. Trying to reduce the prep time/make water changes more convenient. Goes in clear, comes out cloudy after a few weeks. Started researching this issue after inadvertently creating a blizzard in my tank two weeks ago.

I noticed this is not always the case in every jug, and further, seems to be less so during winter months (which does add credibility to the storage temperature theory).

Looking at this article, mixing practices may also come into play: http://www.theaquariumsolution.us/cloudy-h2o-salt-mix

Perhaps adding salt much slower with a more powerful pump, possibly without heating the water could help Ca stay in solution...

Also interesting that valuable elements beyond just Ca could be precipitating out as well...

For someone like me that doesn't dose and depends on water changes for element replacement in a smaller reef, seems like at this point the healthiest options is to mix on demand unless I could store my jugs in the fridge...

 

[disc1]

I have once heard that CO2 diffuses into the water thereby lowering the KH via some reaction. Have you tried completely sealing the container?

This is bad chemistry. The dissolution of CO2 will lower the pH but not affect the alkalinity.

 

[disc1]

and heated to 80 F.

The higher temperature is favoring the precipitation. Calcium carbonate (the stuff that is precipitating) is more soluble at colder temps. Turn the heater off and wait until you are ready to use the water before you heat it. IF the water change is small, you may not even need to worry about warming the water up at all as the temp change to the tank would be small.

This does happen in our tanks as well. It happens because we tend to run alkalinity well above NSW values. If you keep alkalinity between 6 and 7 like NSW you'll find much less precipitation. That's why it tends to bottom out about there. But it does happen in the tank, it's just that the precipitation happens on the sand and the rocks where you can't notice it.

 

[jangy]

I use filtered seawater, but the theory is the same.
From what I'm reading, we are missing the discussion on BUFFER CAPACITY. pH is one thing, but the capacity is key. Without capacity, any external force (in this case, CO2) drives the reaction. With good capacity, it takes a minimum amount /strength of acid to adjust the water's pH.

Fact: Standing Deionized water will go to slightly acidic if exposed to air (CO2).
The reason is that pure water has no buffer capacity and the CO2 converts to a weak acid (similar to citric acid).

The salt mixes have varying degrees of buffers. The base salt doesn't buffer, so it is all about the additives.

If you have low alkalinity, then the weak acid shows it's force. That is what happens in a storage container.

To address the OP on why the containers are different than tanks: I don't see it being due to container materials, but rather to chemistry. The tanks will have stronger buffer capacity AND organic waste processing than will stagnant or even stirred containers.

As far as temperature, I agree with the poster that recommended LOWER temperatures. Colder water will slow CO2 uptake, which will minimize impact to the buffer strength.

 

[shellsea]

The higher temperature is favoring the precipitation. Calcium carbonate (the stuff that is precipitating) is more soluble at colder temps. Turn the heater off and wait until you are ready to use the water before you heat it. IF the water change is small, you may not even need to worry about warming the water up at all as the temp change to the tank would be small.

This does happen in our tanks as well. It happens because we tend to run alkalinity well above NSW values. If you keep alkalinity between 6 and 7 like NSW you'll find much less precipitation. That's why it tends to bottom out about there. But it does happen in the tank, it's just that the precipitation happens on the sand and the rocks where you can't notice it.

Thank you David. solid info, as always. I am removing the heater from my 30 gallon SW storage. I do continuous, (1 gallon per night) changes in total volume of about 120 gal. so that should not be an issue. Right now in Florida the garage is plenty hot anyway. What about the earlier recommendation on the quiescent business. I had to look it up lol but should we also stop circulating and airing the stored SW?

 

[Rahl187]

I'm in Arizona and it gets hot in my garage so I am finding, as chemistry would also concur, that higher temperature would increase solubility. It is because there is more kinetic energy in the molecules breaking up the bonds of the precipitate.

However, I think I have the ultimate solution: Use CO2 like in a Calcium reactor!!! I do not have one so cannot test but since CO2 in a Ca reactor can break up even crushed coral and shells, I think it is safe to assume that CO2 would keep the precipitate from ever forming!

What do you guys think!? Can somebody test this?

 

[dkeller_nc]

I'm in Arizona and it gets hot in my garage so I am finding, as chemistry would also concur, that higher temperature would increase solubility. It is because there is more kinetic energy in the molecules breaking up the bonds of the precipitate.

Not as far as precipitation of calcium carbonate is concerned. You're right that the higher the temperature, the more rapidly a salt will reach its equilibrium concentration in solution. However, with calcium compounds, the equilibrium is shifted toward the solid at higher temperatures. In other words, higher temps = more precipitation.

You're correct that you can acidify saltwater and drastically increase the solubility of calcium carbonate, and thus greatly minimize the precipitation. But if you're going to do this, you might as well use hydrochloric acid to acidify it instead of CO2.

Keep in mind that you will have to raise the alkalinity/pH again with something like sodium hydroxide before you use it. Personally, seems like too much trouble.

 

[SteveFast]

Found this thread and some others that are related. Also notice that Randy and David have responded here before, so here goes on wing and a prayer that someone can provide some guidance to improve what I've experienced. I too am noticing large drops in alkalinity on my stored salt mix. Even though I do not run a heater, yet do have two 500 GPH Hydro's to keep the water moving. Further it is covered... though I suspect neither of those attributes are relevant. I understand that most salts may be unstably high in their calcium-alkalinity combination which may cause drops in both to stable levels. What are stable levels? At what levels to Randy and David keep their systems?


I'm motivated to understand this as I believe it is fundamentally related to what I'm experiencing in my tanks (two 40s and a 120)... or at least my ignorance is related! In my tanks I've tried to keep my dKH in the 8.5 to 9 range, though in order to do so, I have to dose sufficient calcium/alkalinity each day to account for a 2.5 dKh drop per day. If my intended levels are higher than what is sustainable, then that likely means that my doses are mostly precipitating and not biological used... and I'm simply precipitating $. So I imagine that Randy and David have their systems tuned so that their calcium-alkalinity dosing matches the biological need. Randy, I recall reading that you use limewater. Is that true? David, what do you do to maintain calcium-alkalinity levels according to the biological need?


Basically I looking to follow best practices, so I would appreciate any guidance from anyone who has been able to successfully maintain stable levels of magnesium, calcium, and alkalinity and replacing only the amount that is biologically consumed"¦ which I presume is much lower than what I'm dosing.

 

[Rahl187]

And this is stored salt in an otherwise empty tank? But sounds like you are talking about your DT?

 

[SteveFast]

One more thing. In my previous post, I am reasoning that the drops in my storage is the root cause of the drops in my tanks. Especially since the drops are similar in magnitude and all three tanks, despite differences, have similar drops.

 

[SteveFast]

Yes the stored salt water is in a 32 gallon Brute with lid. The raw salt is stored in buckets with lids. I've found this to be true for IO Reef Crystal, Seachem Reef, HW, and Kent salts. Other perhaps irrelevant environmental factors in the room are base temperature of 68 degrees with ~430 ppm of CO2.

 

[SteveFast]

Keep forgetting some perhaps relevant details.. RO/DI water used for the mix... though I'm on a well that, with the drought in PA, is rather dirty.

 

[Rahl187]

How long are you storing the saltwater? To give you an answer from my experience, ummm, well, I pretty much gave up on storing saltwater. Yes, it precipitates, period. More than 24 hrs and I would consider it not usable unless dose it back up to spec. I try to use the water same day, about 4-8 hrs mixed, maybe 12, sometimes even 24 hrs if I get lazy.

I believe that if you truly want to store saltwater long term, you will have to put a sufficient quantity of calcium-carbonate, aka, reef rock, to buffer the system. However, as you mentioned above, this may simply mitigate the situation to some balancing point. However, over time, the precipitation will add to the buffering effect and further mitigate future precipitation. I believe this is why we do not see Alk drops in our aquariums like we do in otherwise empty containers. This method of using reef rock in long term saltwater containment has yet to be tested, as far as I know (well aside from all of our DTs), maybe someday I'll try it but I guess I got over it and just mix as needed.

 

[SteveFast]

Thanks for your thoughts and experiences. Sorry for a delayed response. So for more background... all 3 of my DTs require heavy two part dosing per day to keep the alkalinity stable. The dosing required is enough to account for a 2.5 dKH loss per day. So it was suggested that I check the alkalinity of the water I use in the water changes. That is when I noticed that the alkalinity in my stored SW was dropping too. So, I figured if it was dropping on the stored water, it would also cause some/most of the drop in my DTs. I reasoned that there is nothing in the DTs to prevent it from dropping, so it should. After reading every article Randy has on ReefKeeping, I have not been able to determine a reason for the drop in either the DTs or the storage water... For example in one article it says that nitrate creation could cause it, yet mine are 0. Ditto for phosphates. Magnesium is ~1400. Corals are all softies. Further although two tanks have coralline, the other has none. I also did a few back of the envelop calculations to see how much precipitant I should expect for the alkalinity drop I experience and found that to be ~2 cc in the storage tank... certainly a sufficiently small enough amount that when spread over the available surface area, would be nearly undetectable. The same holds true for precipitants in my DTs. So my hypothesis is that most of my alkalinity is going to undetectable precipitants. This seems odd as my ratios are what Randy posted in this article: http://www.reefkeeping.com/issues/2002-04/rhf/feature/index.php

To say the least, this is frustrating... though given the uniformity of the phenomenon across my tanks, I think it is something environmental or in the water as those are the common factors across all tanks... though now I'm grasping for straws...

 

[SteveFast]

Thanks for your thoughts and experiences. Sorry for a delayed response. So for more background... all 3 of my DTs require heavy two part dosing per day to keep the alkalinity stable. The dosing required is enough to account for a 2.5 dKH loss per day. So it was suggested that I check the alkalinity of the water I use in the water changes. That is when I noticed that the alkalinity in my stored SW was dropping too. It happens even if I only store it overnight. So, I figured if it was dropping on the stored water, it would also cause some/most of the drop in my DTs. I reasoned that there is nothing in the DTs to prevent it from dropping, so it should. After reading every article Randy has on ReefKeeping, I have not been able to determine a reason for the drop in either the DTs or the storage water... For example in one article it says that nitrate creation could cause it, yet mine are 0. Ditto for phosphates. Magnesium is ~1400. Corals are all softies. Further although two tanks have coralline, the other has none. I also did a few back of the envelop calculations to see how much precipitant I should expect for the alkalinity drop I experience and found that to be ~2 cc in the storage tank... certainly a sufficiently small enough amount that when spread over the available surface area, would be nearly undetectable. The same holds true for precipitants in my DTs. So my hypothesis is that most of my alkalinity is going to undetectable precipitants. This seems odd as my ratios are what Randy posted in this article: http://www.reefkeeping.com/issues/2002-04/rhf/feature/index.php


To say the least, this is frustrating... though given the uniformity of the phenomenon across my tanks, I think it is something environmental or in the water as those are the common factors across all tanks... though now I'm grasping for straws...

 

[Rahl187]

How long are you storing saltwater?