How to automatic mixing water

[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.

[wolf_bluejay]

Originally Posted by 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.

Well, the cost of the controller I don't think could be rolled up into, as it has other uses as well. If oyu wanted to just go with some dedicated controller, I don't think the parts would cost more than about $50+ plus the sensor.

And if you went with the "salt and fresh top-off" the salinity of the salt water would no longer matter, as the controller would always work it out in the end. So if you did go with an increased salinity salt water (4x usual) you would only need 50 gal to store the equivalent of 200 gals of water change.
In my case I have a 220 gal tank, so I'm going on the high side of things with that in mind. If you have a 75 gal tank, you could put in a 20 gal salt water tank and hold the equivalent of 80 gals of water change.
Looking at a lot of fancy water change setups using brutte garbage cans, they have 50 gals of RO/DI and 50 gals of salt water ready. having 1.025 salt water handy would eliminate the need to store 50-100 gals or RO/DI water and have a much smaller fresh water tank.

Heck, with the controller taking care of things, you could probably get away with mixing the salt water at something like 1.015 or so, and most of the top-up can come from just the one tank assuming a few gal a day water change. Top up with 1.015 water, pump a bit out, and let evaporation do it's thing.

If you didn't have the controller -- you could (in theory) mix 1.015 water, have a small pump on a timer to remove a gal a few times a day, and have the 1.015 go in as top up. if you could find the right balance, between how much to pump out, and the density to mix up to match your evaporation -- it would work with constant tweaking. I just wouldn't want to have to watch things that closely.

[sphelps]

Are you talking about building a controller for $50? I'm not sure about other controllers but to upgrade a pre-existing profilux to measure salinity you're looking at close to $400 with the sensor, the sensor alone is around $250. A two pump dosing unit to add onto a profilux is around $250 so this would be a cheaper alternative and realistically do the job just as well. I'll admit the salinity measurement is really nice to have as the options for changing and maintaining salinity are endless but I've used these units before and they require a fair bit of attention. I had to adjust the gravity offset every few weeks and often change the set points for the salt control.

If I where to go with a saturated method I would choose the salinity controller but if I was going to go through the trouble of maintaining a large amount of saltwater pre-mixed to match the tank then I would opt for the simplicity of two dosing pumps. Unless the tank was fairly large as dosing pumps would take too long to change a decent amount of water.

[wolf_bluejay]

Originally Posted by sphelps

Are you talking about building a controller for $50? I'm not sure about other controllers but to upgrade a pre-existing profilux to measure salinity you're looking at close to $400 with the sensor, the sensor alone is around $250. A two pump dosing unit to add onto a profilux is around $250 so this would be a cheaper alternative and realistically do the job just as well. I'll admit the salinity measurement is really nice to have as the options for changing and maintaining salinity are endless but I've used these units before and they require a fair bit of attention. I had to adjust the gravity offset every few weeks and often change the set points for the salt control.

If I where to go with a saturated method I would choose the salinity controller but if I was going to go through the trouble of maintaining a large amount of saltwater pre-mixed to match the tank then I would opt for the simplicity of two dosing pumps. Unless the tank was fairly large as dosing pumps would take too long to change a decent amount of water.

The cost I was referring to was to build a simple controller for the salinity only -- not a whole controller -- and the $50 for the parts was an over-estimation. As for the cost of the salinity probe, the hardware is really only worth about $50-$100 for the probe. It would be even cheaper if you didn't bother with the "automatic temperature compensation" and assumed that your tank would not vary from 0-100 degrees.

Most of the profilux and other controllers are really, really pricey for what the hardware inside costs. Similar boards that support sensors, probes, relay outputs, and all the fun stuff are usually under $200 for the whole works. The extra cost is for making it pretty, including programming software, and customer support.

As for the peristaltic pump -- I just don't think they are quite up to the task of moving 50 gal a week of water. These pump are built to part time, and moving small amounts of water accurately. replacing a $250 pump about once a year adds up quickly.


I think that most of this was relating to the larger tanks, and larger equipment rooms/areas as I don't think I would go through the hassle of auto water changes on a 30 gal tank. I assumed that most people looking at this were in the same boat as me -- where doing 20-30 gal water changes a week just doesn't work with a bucket. If I could do my whole water change using 2 old salt buckets, I would go that way. But when you need 30-40 gal tubs just to mix the water -- 200 gal of water storage isn't too crazy when you have a 200+ gal tank and all the other gear that goes with it.

[lastlight]

Originally Posted by 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.

Yeah it's not practical for most but I'm designing a fishroom and may create a spot for one.

[abcha0s]

I'm going with the ~200 gallon storage container. I'm looking at the LiterMeter III peristaltic dosing pumps for the Continuous Water Change. The pumps are calibrated by volume, rather than time so minor differences in pressure can be accomodated. The ATO runs independantly and has nothing to do with the water change system. It's an incredibly simple system.

However, the purpose of my post was to share my experience with salinity probes. They are increadibly sensative to stray voltages and tend to wander all over the place. Curt at Apex recommends that the salinity probe be placed in a drip cup to completely issolate it from the sytem. I was never able to get a consistant reading from my probe and basically threw it out.

Another concern is the mixing rate of new saltwater coming in with tank water. I use this concept to monitor the pH of my system when topping up with Kalk saturated water. I have the controller set to shutoff the Kalk ATO when the pH hits 8.4 - However, by the time the pH sensor reads 8.4 the pH in my tank is past 8.5 - There is a delay in the reading but it's also partly how the kalk saturated water mixes into the tank and where the probe is located.

IMHO - I wouldn't trust a sensor to control/maintain the salinity in my tank. I think that you will be constantly adjusting minor fluctations in salinity either up or down. If your not careful, you may get a bouncing effect.

I also woudn't trust a cheap dosing pump. Thus, I'm prepared to spend the money for a high quality balanced pump setup.

[wolf_bluejay]

Originally Posted by abcha0s

However, the purpose of my post was to share my experience with salinity probes. They are increadibly sensative to stray voltages and tend to wander all over the place. Curt at Apex recommends that the salinity probe be placed in a drip cup to completely issolate it from the sytem. I was never able to get a consistant reading from my probe and basically threw it out.


IMHO - I wouldn't trust a sensor to control/maintain the salinity in my tank. I think that you will be constantly adjusting minor fluctations in salinity either up or down. If your not careful, you may get a bouncing effect.

I also woudn't trust a cheap dosing pump. Thus, I'm prepared to spend the money for a high quality balanced pump setup.

Grumble, grumble -- Ok, I have to admit, you are right on this -- a lot of the idea of using the controller really depends on getting a probe that accurately measures things. The delay in measurements is not a big deal as you could just have delays put into the pump cycle -- pump for a minute or 2 -- wait 10 -- check ph, repeat.

But I could see most of these probes being affected by stray voltage, calibration drift, and general crappiness that would cause the system to mess up the tank parameters big time.



Has anyone done the math on how much the salinity would be affected over time by not using "matched" pumps? If oyu have 200 gal tank, doing 2 gal a day water change, and the pumps are out by a bit --- how much would things get out of whack over the whole ~200 gal water change?