weird question about mixing salt

[Eric Max]

Two questions, answer first then bash me later. :hammer:

i heard that mixing up salt in a bucket and dumping it in a system with fish/corals can be toxic. Is this true, and if it is, why?


now a dumb question-- I was mixing salt with RO water using my hand and the clumps of salt were starting to feel pretty warm before they dissolved. Why is this?

[SJimmyH]

Different chemicals give off heat when they dissolve. No problem, this is normal.

You are going to get different answers for the first question.

Some people mix it and let it sit for days prior to use. I have never seen the need to do this. IMO, make sure the salt is mixed well and completely dissolved. Not sure what they all believe will occur by letting it sit or mix after that, but I think its just fine.

My corals and fish have never seemed to mind.

[Henry Bowman]

I dont think that there is anything "toxic" about mixing salt water and how quickly it is added to the tank but I do think a reefkeeper can make some mistakes by not making sure the new water is set up for a stress free accurate process....

I start with a basic recipe of salt to RODI to start mixing. I run a powerhead and small heater (sometimes overnight) to make sure the salt water is at the same temp as my tank then adjust the specific gravity if needed.
Then I add a Ca supplement before I do a water change. I never see any negative impact from a water change.

SG will change based on temp. Corals and Fish could be negatively impacted by drastic temp and salinity changes...

My .02 cents FWIW

[BLockamon]

I've heard that salt water needs to properly aerate before the pH buffers correctly in the 8.1--8.3 range (maybe as a result of the type of carbonate salts used in the mix). I've never tested this, however. In any case, if I'm doing a large water change, I always heat and aerate. I have sometimes added small amounts <5% of the tank volume without letting it sit.

[Eric Max]

thanks a lot for your info guys. i always mix up saltwater ahead of time (heated and kept agitated with an air stone) for whenever water is needed.

if anyone else has other thoughts on this, let me know because i love reading this stuff!! :D

[drummereef]

Freshly made up saltwater has trace ammounts of ammonia. This is why it is proper to let the saltwater 'age' for 12-24 hours before adding it to the tank. ;)

[thejrc]

I think the reason for not dumping is possible shock due to temp / ph / salinity change... which makes sense. I mix mine up in a bucket, sometimes days before, sometimes an hour before... either when I do it I think it's the way that counts. I use a pump in the bucket to help mix, and swirl it around as much as possible. I test SG twice before pumping it into the tank. If I pump I clip the hose so it sprays along the top of the front wall of the tank, none of the water hits corals and it allows for good dispersion even with my pumps off. If I pour, I always pour into my sump. Since pouring into the sump is a pain I typically just pump it in nice and slow.

If I have water that I made a while ago (RO takes a while) I usually test it when I test whatever current batch I'm working on. This lets me keep 20 gallons or so of ready replacement water handy that I know is close to if not right on my target SG.

Not sure about ammonia as drummer pointed out, but I do see the possibilities of all kinds of odd chemical reactions. I havent run into the heat thing but knowing how potassium and other chemicals work with water I could see that too.

In short 5 gallon buckets are cheap, the rinsed out kitty litter buckets I use are not only cheaper but always available (as cat's poop you know). having extra prepared water on hand not only makes water changes easier but it helps in the event of an emergency (imagine having to do a 50% water change NOW..... are you ready? 25%? 10%?). let it stock up, test before you pump it in and you should be well off

[wan 2 B reef'in]

... OK here goes my .02 cents.... What I've heard about mixing up some water is that salt by itself is caustic, which would answer the warm sensation on your hand/s.
The reason for letting it sit is so that your fish don't get the same warm or burning sensation you get, as it suppossedly remains caustic for at least 24hrs, I myself at times have mixed up water and added it not long after mixing it once I reached my target SG with no ill effects, but now I do try to let the water sit at least 24hrs before adding it since I heard the "caustic" claim.

[reefnetworth]

i mix mine for 24 hrs minimum with a powerhead. match the parameters (IO & Part-2) as close as possible. when i do a WC nothing seems to change except the anemone which i figure is typical since it has two clowns driving it nuts. :lol:

JDM :cool:

[acroporas]

I dump the water into the aquarium as soon as I can see the bottom of the bucket.

It may not be the best way to do it, but I have never seen anything react negatively from doing it this way.

[Eric Max]

wow... some great info here. thanks a lot you guys

[Billybeau1]

The main reason to aerate the water for awhile is to allow the water to reach equilibrium in regards to CO2. Of course small water changes do not have much affect, but with larger water changes, this becomes more important. I do 20% water changes every two weeks and let my water aerate for a minimum 12 hrs before using.

Drumm, There should not be any ammonia in freshly mixed salt water. :)

[aznlmpulse]

I dump the bucket in small undissolved particles and all as long as my s.g and temp matches. Hahaha. :D

[wooden_reefer]

The warming effect when dissolving salt is called heat of dilution in chemistry. It can be explained by the Second Law of thermodynamics, entropy.

The most striking is that of sulfuric acid. That is why you never add water to concentrated H2SO4, you add the H2SO4 to water. If not it would boil and splash and really hurt you.

Concentrated H2SO4 is used to unclog drains, so be careful.

As far is fish is concerned, I routinely use salt water prepared from salt mix just 15 minutes earlier, even when it is a bit cloudy.

I do so only for salt that looks dry and very free-running, but not when it is lumpy. I can't tell you why, but some one told me so. For salt that is lumpy, I wait about a day for the last bit to dissolve.

[acroporas]

<a href=showthread.php?s=&postid=10267535#post10267535 target=_blank>Originally posted</a> by wooden_reefer
The warming effect when dissolving salt is called heat of dilution in chemistry. It can be explained by the Second Law of thermodynamics, entropy.


I'm pretty sure that the heat is released is the result of the effect of dissolution rather than dilution.

I suspect the heat is mostly coming from the type of Calcium used. Mix some Kent Turbo-calcium in water and see how hot it gets.

Also you should note that different salt mixes release different ammouts of heat (probably because of using a different form calcium). For example, instant ocean does not warm noticably, while tropic marine does.

[bertoni]

"Heat of dissolution" is a fine term, and the effect is more pronounced with anhydrous calcium chloride. The hydrated version doesn't have so much heat to release. :) Or should I say the enthalpic content is different.

[wooden_reefer]

Yes, I mean the same.

Heat of dissolution is about the same as heat of dilution.

I just wanted to clarify that it is a natural phenomenon. Not caustic effect.

It is about going from a state of more order to more random. Second Law.

[wooden_reefer]

Heat of dissolution is more enthalpic as it involves bond rearrangement. First Law

Heat of dilution is entropic Second Law

I think this better.

The main point is that the heat is natural and is not that the salt is caustic.

[loosecannon]

I use tap water and stress coat in one gal. jugs Air stone for one week, that`s my r.o. water. Than I mix reef crystals in a 5 gal. buckett with air stone 1200 maxi jet power head, and heater for one week than stor water on till needed.

[Eric Max]

this is getting real nice. i love learning about reactions (especially ones related to saltwater aquariums). you guys are making the answer to this question much more interesting then i had anticipated. Thanks!