Salinity based ATO?

[Osric]

As part of my complete automation project I've been planning to do salinity control and ATO. I realized recently I could combine these two and am interested in people's opinions on whether this has been done and whether it'll work well or not.

 

In my sump, I'll have a high-water-mark float switch and a low-water-mark float switch, to avoid draining too much water or putting in so much that the system could flood. The sump will also be equipped with a pump for water changes plumbed to the sewer system.

 

I plan to have a salt slurry reservoir with water well above 35ppt, and a clear reservoir with RO/DI water for topoff. So instead of having a standard ATO from there to the sump, I was debating having the salinity reading from the sump trigger the addition of some salt slurry (when the salinity reads too low) or some RO/DI (when the salinity reads too high). The monitoring looks like this:

 

if salinity too high -> add RO/DI for 30s

else if salinity too low -> add salt slurry for 30s

else if low-water-mark -> add RO/DI for 30s

else if high-water-mark -> drain water to sewer until low-water-mark or 5m, whichever is first

wait for 4 hours, then repeat

 

Naturally the times could be different depending on the pump sizes and so on, but this will keep the salinity bouncing gently around 35ppt and ensure the water level is never below the low water mark (or above the high mark).

 

A water change can be built around this too, since this has the behaviour of draining water into the sewer all that's needed is to load the system with water above the high-water mark. A separate routine can take care of doing that alternating between salt slurry and fresh RO/DI.

 

Opinions?

 

Osric

[patback]

Your salinity will never be to low if you test before doing water changes. Smaller amounts of water in the ato container will keep it from pumping too much. A gallon Into 15 gallons of salt will barely nudge your salinity and would be fine. 3 gallons is a good size for most nanos with a sump.

Keeping a "watery salt" mix instead of saltwater is also a terrible idea. Water can only hold so many things before it "drops" it out. All of your parameters as far as calcium,magnesium,iron , iodine, etc will be negatively affected, and I can see your salt ato and fresh ato fighting each other wasting money, salt, and your nice floors you have.

 

Maybe I misread it, but the closest thing I have heard of working was someone having a controller filling mixed saltwater into the sump and having it over flow to a drain nearby.

[Osric]

Technically ATO can drive salinity down depending on how the skimmer is adjusted. With wet skimmate and high evaporation, your skimmer will draw out salt and the ATO won't replace it. 'Course this would take a long time.

 

The idea that the elements would fall out of solution is interesting. Do you have any data to show at what concentrations that'd be a problem?

 

I don't think overflow will be an issue. For this post I've described it as a pump but I plan to defend the sump against overflow with a CSD plumbed into the drain.

 

Osric

[patback]

Technically ATO can drive salinity down depending on how the skimmer is adjusted. With wet skimmate and high evaporation, your skimmer will draw out salt and the ATO won't replace it. 'Course this would take a long time.

 

The idea that the elements would fall out of solution is interesting. Do you have any data to show at what concentrations that'd be a problem?

 

I don't think overflow will be an issue. For this post I've described it as a pump but I plan to defend the sump against overflow with a CSD plumbed into the drain.

 

Osric

 

 

I'll try to find it. When I first started out I read an amazing article on mixing water and water changes. I hope I can find it again... It was over a year ago that I've read it.

 

What size is your skimmer out of curiosity, and how often do you plan water changes? As long as the skimmer isn't huge, the salinty should never get out of a sweet spot as you could tweak it during weekly maintenance.

[Osric]

What size is your skimmer out of curiosity, and how often do you plan water changes? As long as the skimmer isn't huge, the salinty should never get out of a sweet spot as you could tweak it during weekly maintenance.

 

I'll be using an Aqua C EV120 skimmer (I am still waiting for it to arrive; it and the sump are new additions). Total water volume about 55-60 gallons.

 

As I mentioned this is part of a plan to completely automate tank maintenance. I was thinking of having the system change 1-2 gallons daily.

 

Osric

[funkyfish77]

[quote name='Osric' date='Oct 21 2012, 12:46 AM' post='4

 

As I mentioned this is part of a plan to completely automate tank maintenance. I was thinking of having the system change 1-2 gallons daily.

 

Osric

 

If you don't mind sharing what controller are you going to use? I'm putting together a touch screen arduino for my tank

So controller based thing are high on my interests. How are you planning on monitoring salinity any link for your probe you will be using?

 

Funky

[Osric]

If you don't mind sharing what controller are you going to use? I'm putting together a touch screen arduino for my tank

 

I'm using an Arduino Mega with the two-line text only display kit from Adafruit. The salinity probe and stamp are the ones from Atlas Scientific.

 

I plan to build my own pH circuit but have the one from Atlas for double checking my work. I have a separate thread where I was planning to document my DIY controller.

 

At the moment I'm still in the middle of the bean animal inspired PVC overflow. As I type I finally have that working nicely, can hear a tiny trickle of water but I think that's actually the water going from the display into the rear chambers of the Solana.

 

Osric

[Salty_Snack]

Terrible Terrible Terrible idea!

 

Why would you try to take something rather simple and overcomplicate it to such a degree? The amount of salt lost to a skimmer is minor for most all systems, even when skimming wet. If your really worried about it set your water change water to a slightly higher salinity. Say 1.025 if your running your tank at 1.024.

 

Salinity probes are typically inaccurate over long periods of time which means you would need to recalibrate it regularly to keep your monstrosity of a system running correctly.

 

I do like the idea of an auto water change system, but I would rather do it on demand rather then automatically.

 

Again, your really need to rethink this.

[Osric]

Salinity probes are typically inaccurate over long periods of time which means you would need to recalibrate it regularly to keep your monstrosity of a system running correctly.

 

Atlas claims their probe can run continuously for 12 months before needing recalibration. What's a more realistic expectation?

 

Clearly I could go with just top-off, and have a separate system for water changes. But presumably then I'd need to mix my water change water manually to get the right salinity, if I can't trust the sensor long term.

 

Osric

[fwadiver]

you salt slurry would need to be heated and mixed too = lots of calcium carbonate plating your heater... There really is no way I can see getting around using a refractometer, I used the $1000 equivilant of one of those salinity probes in an experiment once, we were lucky if it held its calibration for more than a week. noted that you dont need .1% accuracy, but the problem is it tended to constantly drift in one direction... which is going to drive your salinity one way over time. Basically you could do this, but you wouldn't be able to trust it and would always be checking on it.. or at least i would, which removes the appeal of it being automatic.