My auto-mixing auto-water-change station. Seeking for comments.

[DerekC]

Here is my auto-mixing station that also does the daily water change automatically.

All I do is dumping salt (2 boxes capable of providing 200 gallon mix) at the upper tank every couple months or so.
I use 1 EB832, 1 PM2, 1 cond probe, 1 breakout box, 2 pmups, couple powerheads, 3 RO solenoids, 2 float valves, 2 recirculating pump, 2 filter socks.
2 float valves are connected to my RO line and installed on the upper (brine) tank and lower (1.025 SG) freshly mixed tank. They are turned on by 2 solenoids.
1 solenoid is installed in the siphon tubing from upper tank to lower tank.
One pmup pumping freshly mixed water to my display tank for 1 hr a day (15 gallon?) and at the same time one pmup (connected to the EB832 at the display) pumps old water out of display.
While doing water change, apex also turns on off the siphon solenoid to drip brine into the lower tank and turns on off solenoid to let RO into the lower tank depending on the SALT reading by the probe. That way, lower tank is always at 1.025 SG. The solenoid to let RO into upper tank is on during water change.
So, there is always about 30 gallon of freshly mixed saltwater ready to serve.
There is a heater (set to 72F) that so far never got turned on.
There are multiple float switches, overflow pipe to detect / avoid emergencies.
There is a pump pumping water from lower tank to upper tank so that I don't have to manually do it for some occasions.
There is another pump at the lower tank pumping water into a 7" filter just in case there is any precipitate of any kind.
Tanks are 40G breeders. Shelving is from Home depot (or Lowes). Overall maybe $700 at most. When manual water change is eliminated, I enjoy reefkeeping (or fishkeeping) a bit more.

Just wanted to share and if u see any issue or anywhere I can improve, please fee free to comment...

 

[a.t.t.r]

@Randy Holmes-Farley might wanna comment on this.

you are using salt mix to make a extremely dense brine. It is possible things will precipitate out of solution and while your end salt mix may be the correct salinity it may contain improper ratios of the different salts. For example I know magnesium comes out of solution really easily.

 

[DerekC]

Precipitate. That is what I saw at the bottom of brine tank. A lot of white slushy powder.
So, I am incorrectly mixing salt? What am I missing? What is that precipitate? Maybe I should do a ICP test.
@Randy Holmes-Farley, or any more experts can pls comment?

 

[ColoredRock]

 

[Gtinnel]

As mentioned it's not recommended to make an extremely high salinity mixture because certain elements precipitate out.

 

[a.t.t.r]

The

Precipitate. That is what I saw at the bottom of brine tank. A lot of white slushy powder.
So, I am incorrectly mixing salt? What am I missing? What is that precipitate? Maybe I should do a ICP test.
@Randy Holmes-Farley, or any more experts can pls commen

Depending on what happens during it coming out of solution it may be able to redisolve like normal or may have changed entirely (like forming calcium carbonate that will not redisolve). You can not mix a brine solution past saturation and expect element ratios to stay the same. Think of why two and three part additive are separated and what happens if you put them into a single container.

I think you need to rethink your design from the ground up and find a way to deliver dry salt into your mixing tank instead (and also make sure the salt is homogenous (I think that’s the right word…) in its dry state)

 

[a.t.t.r]

Maybe let it run two cycles then do a water test on the bottom tanks water.
It maybe possible if your salt tank is mixed enough that nothing settles that the precipitated stuff could stay in suspension and redissolve in the bottom tank. Inotherwords nothing can settle on bottom of top tank.
And that is assuming stuff only came out of solution and did not chemically change

 

[coralfishreef]

For the top tank, with the tank empty, add RODI water until near full - leave enough room for the salt. Add salt and mix the top tank to the desired salinity, let rest per manufacture instructions, double check salinity, and then fill the bottom tank from the top tank. Use the mixed water in the top tank to fill the bottom tank until the top tank is empty and then repeat.

 

[a.t.t.r]

For the top tank, with the tank empty, add RODI water until near full - leave enough room for the salt. Add salt and mix the top tank to the desired salinity, let rest per manufacture instructions, double check salinity, and then fill the bottom tank from the top tank. Use the mixed water in the top tank to fill the bottom tank until the top tank is empty and then repeat.

That removes the point of the top tank. They are trying to make 200+ gallons of salt in a space of 40 gallons.

 

[DerekC]

Ok. Getting a ICP test done with the bottom tank water.
The powerhead at the upper tank is powerful enough to keep the precipitate suspended (hence it is all white) but I have the siphon tubing into a 5 micron filter sock so that the solenoid does not get clogged up... That means precipitate does not go down.Let me change to a 200 micron filter and see what happens.

 

[Joe31415]

Getting a ICP test done with the bottom tank water.

But you have to have a control to compare it to. Really and truly, you should also do an ICP test on some of the same salt (the same batch/bag/bucket would be even better) mixed properly.
With just the single test, it'll be hard to tell if something being high or low is due to your mixing method or the salt. If everything comes back, more or less, the same, you can be relativity* confident that your method is acceptable.

*As I think about it more, you'll have to keep in mind that since the potential issue here is things precipitating out, the age and storage conditions of the brine may play a roll. That is, 1.025 water made from freshly made brine (200g salt mix/30g water) may be different today vs the same thing but letting the brine circulate with a powerhead and heater for a week. Similarly, the first batch of 1.025 water you make might be different than the last batch you get out of the brine as there's more RODI for some things to dissolve back into solution.

 

[a.t.t.r]

Ok. Getting a ICP test done with the bottom tank water.
The powerhead at the upper tank is powerful enough to keep the precipitate suspended (hence it is all white) but I have the siphon tubing into a 5 micron filter sock so that the solenoid does not get clogged up... That means precipitate does not go down.Let me change to a 200 micron filter and see what happens.

Doesn’t icp only test for elements and not what form they are in. So free calcium salts comeback the same as calcium carbonate ?

 

[DerekC]

Time to start looking / fabricating some sort of automatic / controlled dry salt gravity dispenser.

 

[a.t.t.r]

Time to start looking / fabricating some sort of automatic / controlled dry salt gravity dispenser.

Since you already measure the salinity you could do an auger type system. A long drill bit into a piece of pvc held at a shallow angle.

Could also look into compressed air to move the salt in a 1/2 inch tube injecting the air into a t at one end and have that sit connected to a salt bucket.

 

[DerekC]

Right. or some worm gear driven opening.... 3D printed unless there is such ready-made product on the market. Somehow turning on an outlet for x sec will dump some amount of salt, via a funnel or something... More or less like the auto feeder...

 

[a.t.t.r]

Right. or some worm gear driven opening.... 3D printed unless there is such ready-made product on the market. Somehow turning on an outlet for x sec will dump some amount of salt, via a funnel or something... More or less like the auto feeder...

I would be worried about it clogging under the weight. What about a screw drive horizontal at the bottom of a hopper. There is a reason screw drives are used way more often then other designs.

 

[DerekC]

For now, hope I don't have a precipitate problem.
It will be fun to figure out a way to do automated dry salt mixing that gives us a station with minimal footprint. That would be revolutionary.

 

[a.t.t.r]

For now, hope I don't have a precipitate problem.
It will be fun to figure out a way to do automated dry salt mixing that gives us a station with minimal footprint. That would be revolutionary.

Could do a gallon at a time and do it by weight. There is apx 0.3lbs difference between fresh and sea water.
This could be a really fun project.

 

[DerekC]

ICP results are in for the freshly mixed water. See below.
This is not the display tank water. I use Fritz Reef Pro Mix (red box).
Does it mean my method of mixing (that causes all the precipitate) is not right?

https://lab.atiaquaristik.com/publicAnalysis/142991

 

[a.t.t.r]

You would really have to test a correctly mixed batch mixed to same salinity and compare.

Also these test don’t test what form the elements are in only if they exist. They may not be in a useable form anymore.