How to automatic mixing water

[wolf_bluejay]

Originally Posted by sphelps

Ensuring some salt always remains undissolved insures the salt solution is at max saturation and with constant temperature you can be sure the the salinity of the make up is consistent (max saturation at given temp). You could also in theory measure the salinity and keep it constant however it can be difficult to measure salinity of saturated saltwater and it's easier to just simply look for undissolved salt. It makes other options easier to employ as well. This is of course only important without the use of controllers, a controller eliminates the need to maintain constant salinity in make up water.

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.


Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.

[golf nut]

Originally Posted by wolf_bluejay

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.

So how would you make a good solution that could be handled ?

[golf nut]

Originally Posted by wolf_bluejay

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.


Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.

This is a real question, I respect your expertise, what would be a better method?

[wolf_bluejay]

Originally Posted by golf nut

This is a real question, I respect your expertise, what would be a better method?

Sorry for the delay in responding -- been away a few days again

If you want to get really, really particular you could look up the solubility of each "ingredient" in the mix, and from the ration in the mix figure out how dense you could go.
Off the top of my head, I would be that it would be the calcium. as it is already super saturated in NSW anyways (magnesium is what allows this). As you start pushing the salinity to 2 or 3 times the normal amount, you could expect to see calcium precipitate out onto pump, glass, and everything in the super saturated hold tank. It will also push the equilibrium of the carbonate and probably cause issues with the buffering ("chalk" precipitate)

If you have a calcium reactor, or some cheap way of replacing the calcium you should be OK as most of the stuff in there does have a high solubility. Just always expect your salt mix to be very low in calcium and add as needed. If you are buying the super expensive salt with NSW levels of calcium, they you are wasting a lot of cash. IO salt is typically low on calcium and low in magnesium as well.

The best way, would be to not over saturate your salt as I'm not sure what else would go a little out of whack.

I'm almost thinking that the easiest and best way of doing this, is to just mix up a ridiculous amount of salt water at a time and do the "2 balanced pumps" to handle the water change -- mostly because I do add magnesium, some buffer, and calcium to get my cheap salt up to par and this might be easier with a larger volume of water. IE: 200 gal salt water storage in the basement and just change a few gal a day.
I don't think the salinity could get to out, and with a controller, you could just add some salt water instead of fresh to raise, or pump out a bit and add fresh to lower the salinity...... This way, you wouldn't really care what the salinity in the storage tank was (high or low) and let the controller work it out for you.

[sphelps]

Originally Posted by wolf_bluejay

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.


Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.

Yes this was my original concern with the method as well. However as mentioned I tested it long term on a reef tank with good success. I did not experience any precipitate and the levels in the display remained as consistent as the previous method of manually mixing and changing water.

When you think about it, it's no better or worse than how water is traditionally changed. Most people don't mix a full bucket of salt at once to insure optimal levels. Instead they grab a few scopes here and there which can result in different levels each time.

[lastlight]

Yeah I'd love to be abler to mix up a full pail and then use 10g/week. Not sure having it mixing that long would have any ill-effects. It'd take me months to use it all right now.

I will use a pail a month with the new tank though. This might be the way to go. Params should always be consistent.

[golf nut]

Different manufactures have different method of producing salt, some will give you a pail of 200 white ping pong balls with 2 red ones 4 blue ones and 3 green ones, when all mixed you will have the correct proportions, but mixing in small batches could become problematic. I believe Tropic Marin has a method to give a perfect mix no mater how small a scoop you chose to mix.
I think Farley proved that doing daily changes was just as effective as mass changes, too much math involved for me to want to figure that one out.

Now all we have to figure out is the cheapest method of removing and exchanging a known quantity and put it on a timer to get the correct daily amount no matter what size tank you have.

[wolf_bluejay]

Originally Posted by golf nut

Different manufactures have different method of producing salt, some will give you a pail of 200 white ping pong balls with 2 red ones 4 blue ones and 3 green ones, when all mixed you will have the correct proportions, but mixing in small batches could become problematic. I believe Tropic Marin has a method to give a perfect mix no mater how small a scoop you chose to mix.
I think Farley proved that doing daily changes was just as effective as mass changes, too much math involved for me to want to figure that one out.

Now all we have to figure out is the cheapest method of removing and exchanging a known quantity and put it on a timer to get the correct daily amount no matter what size tank you have.

The more and more I think about it -- the more I'm convinced mixing large quantities at a time is better.

If you used a tall poly container 150-200 gal wouldn't take up much space, and I don't think you would need a large RO/DI reservoir anymore. Most people keep large amounts of RO water on hand for "emergencies", but having 200 gal of ready to go salt water I think would be even better.

As for testing -- I don't test my mixed water change water for anything other than specific gravity, as testing 25 gals at a time for alk, calcium, magnesium, etc would just be to much cost and a pain. But mixing 200 and testing it all at once would give a nice consistent result and would be easy to add calcium and buffer as needed.


As for the pumping -- I think that doing this with logic would be much easier than dealing with 2 pumps that you will never, ever get to be a perfect match without spending silly amounts of money.

For those than can follow controller logic:

1) pump in 2 gals, roughly
2) measure sality


repeat until just right (

if low -- do nothing and wait for some evaporation
if high add fresh slowly,

if just right -- pump out 2 gals, roughly

Basically, you remove some water and have 2 different "top-up" tanks, one salt and one fresh. Mix both to get things just right all the time, instead of having only a fresh water top-off.


If you get the mixing of the salt and fresh right on the controller, your change volume is controlled by how long you run the pump, and the system will "top-off" with the right mix of salt and fresh to re-fill the tank.

[lastlight]

So do you guys think it's ok to have a 200g reservoir of ready-to-go saltwater on hand? Let's say it gets fully used up in a month...

[sphelps]

I don't think it's reasonable to assume most can store 200 gallons of water, I've seen a 200 gallon poly tank and it's big and I can't see many people finding a convenient location for it. Some would even have trouble getting it inside.

Also 2 pumps could work and do work, most use dosing pumps which yes cost more than typical pumps but don't forget a controller with programmable logic and salinity control will run for at least $1000 so it's certainly not a cheaper option but I would agree it's a better one.