Automatic salt adder - ideas

[karimwassef]

I've been looking for a very simple and cheap method to add salt into my aux sump/mixing station.

The posts are very ingenious with hoppers, augers, pinchers, funnels, moisture barriers, etc... Most are targeted at exact measures of salt and avoiding moisture in the dry salt.

I have a different approach that is deliberately the opposite and I wanted to get some feedback.

A bucket with an overflow pipe close to the top filled with dry salt and a little RODI water. Above the salt is a sprayer (or maybe just a hose into the salt) that goes through the bucket top to a valve.

I use my Apex and conductivity monitor to control the length of time new RODI water is added: add for 10 sec, wait for 5 mins. Check salinity, repeat until desired salinity achieved. The water that overflows isn't perfectly mixed, but is saltier than my tank water.

So... Why wouldn't that work?

Optional:
Low rpm motor mixer.
Baffles to the overflow.
Tank sump overflow to drain (we'll call this an auto-changer)

The inspiration here comes from my whole house water softener. It uses salt to recharge the resin and goes through a rinse cycle at night. It's essentially a big bucket full of salty water that gets filled, overflows and needs more salt. Maintenance is 'add more salt'.

[karimwassef]

[salty joe]

IDK this for a fact, but I've read that it's critical to add salt to water, not water to salt. Otherwise parts of the salt mix won't dissolve.

I hope to be mistaken because that's a neat idea. Randy would know-might be worth a trip to the chemistry forum.

[karimwassef]

I could make this into a supersaturated slurry.

[karimwassef]

It resembles my kalk reactor but on a massive scale - somewhat

http://youtu.be/aDFeZ4ZPxrw

[jamie1981]

Don't think it's a good idea adding small amounts of water to large amounts of salt and think that you will get a good even mixture. I'm not 100% but I think you will get calcium precipitation among other things from the ultra high salinity of the slurry. You need to add salt to water not the other way around.

[woodnaquanut]

Originally Posted by jamie1981

Don't think it's a good idea adding small amounts of water to large amounts of salt and think that you will get a good even mixture. I'm not 100% but I think you will get calcium precipitation among other things from the ultra high salinity of the slurry. You need to add salt to water not the other way around.

+1.

Some parts of the salt might not dissolve, others will dissolve and recombine to precipitate out into insoluble compounds.

If you doubt this, try it with one cup of salt.

If you used something like the ESV salt (CaCl, MgSO4) it might work. Of course you'll be 'dosing' four things with this method.

[karimwassef]

Would keeping the slurry warm in an insulated bucket work? What salinity and temperature would work? How about keeping it slightly acidic?

[Raul-7]

Wouldn't this be more hassle than the old fashioned way (ie. adding salt manually and powerhead)?

[karimwassef]

I travel and need to automate as much as possible.

[zachts]

the slurry method was discussed on the chemestry forum. It will not work. Only way to supper concentrate your salt mix and automate is to mix solutions of each component and keep them separate until combining and diluting into RO/DI water to make fresh mixed salt water for your water change.

The dry mixing methods are the only ones I've seen that look reasonably practical but I've yet to see one that makes sense when the complexity and cost is weighted against just having a 50 gallon barrel and dumping a bag of salt in once a month and mixing........

[karimwassef]

My problem is that I have a 700gal system, a 100 gal RODI reservoir, a 100 gal aux sump I use for mixing salt (among other uses). That leaves no room for a salt water reservoir. Even if I wanted to, it would need to be 100 gal at a minimum.

Dry or slurry are the only options given my space constraints (only one garage, LOL).

[zachts]

If all you are using your auxilary sump for is mixing salt water why not use that? how long do you need water changes to go unatended? how many gallons per day can you get by with at a minimum and then do a catchup water change when you return if needed? With good filtration and dosing, water changes should be able to be kept to a minimum.

Then again if your not home and using your garage could the saltwater reservoir be something that you setup before leaving and then empty and store out of the way when you return?

[muttley000]

I'm imagining an auger that is programmed to only run a small amount of salt mix in and then allows sufficient time for mixing/sensing before running again.

[karimwassef]

Here's the scenario -

It's winter, evaporation is lower than usual.
I'm adding kalk mix to increase Alk and pH.
With low evaporation, my salinity is dropping.
It's dropped the equivalent of a 50gal bag of salt.

I'm on the other side of the planet and my wife hates the aquarium and won't touch it with a 10ft pole. If everything dies- good riddance (ok ok. Too much detail).

If only - I had a way to add salt with my Apex. Preferably something smaller than a trash and under $100.

Better yet - what if it self-adjusted....

[zachts]

Are you skimming really wet? What's removing the salt? Salinity shouldn't drop noticeably especially on a tank that large, unless you're removing A LOT of saltwater and replacing with only RO/DI.

To drop that much something would have needed to remove 50 gallons of saltwater.

I used to only do water changes about every two months when I was really busy with work, granted it was only a 55 gallon. Corals started looking a little poor but never lost anything and salinity never shifted more than 0.001 from skimming.

[zachts]

.....might be worth hiring someone from one of the LFS to come and do ocasional maintenance for you.......pretty inexpensive in the grand scheme of things and for peace of mind that someone who knows what they are doing is looking in on your tank.

[karimwassef]

I do skim wet, but the salinity drop also comes from an increase in fresh water being added through nearly kalk additions.

[zachts]

Where is the saltwater going though? Do you have an overflow on your sump or something that is dumping tank water? I find it hard to believe the skimmer could remove that much, I guess it is possible though, you might need to dial it down for a dryer skim.

If Kalk isn't doing it alone you might want to add a CA reactor or 2part dosing to help keep levels up without needing to add so much fresh water to the tank?

[woodnaquanut]

Originally Posted by zachts

Where is the saltwater going though? Do you have an overflow on your sump or something that is dumping tank water? I find it hard to believe the skimmer could remove that much, I guess it is possible though, you might need to dial it down for a dryer skim.

+1

Evaporation is only FW so where is the salt going? If you are not draining off the SW then there should be an increase in total water volume to account for the lowering of SG.

Do you get lots of salt creep? Like pounds of salt creep!

[zachts]

In theory if only the skimmer is removing liquid it would need to remove about 50 gallons worth of skimmate to account for needing to add 50 gallons worth of salt mix.......

[karimwassef]

Yes. I have been skimming about 2 quarts a day, 3 gallons a week or 6 gallons per trip. I also have a sump overflow into the drain so the fresh water buildup pushes saltwater out.

[karimwassef]

Either that or my very expensive conductivity probe is nuts...

[woodnaquanut]

Originally Posted by karimwassef

Yes. I have been skimming about 2 quarts a day, 3 gallons a week or 6 gallons per trip. I also have a sump overflow into the drain so the fresh water buildup pushes saltwater out.

Skimming would, at that rate, take 16+ weeks to drain off 50g. The sump overflow is probably the real issue. You're not replacing evap but actually pushing a given volume of TO per day, right?

Seems like it would be a lot easier to either supplement Kalk with two part or dose a higher concentration of Kalk instead of mucking around with salt mix. Then you could just TO. Easy peezy.

[karimwassef]

I'm pretty sure I'm saturated in my kalk dosing (2lb of powder in 3gal of water).

Let's call my constant export of saltwater "an automatic water changer".

Now... Adding salt as a slurry looks out, so back to difficult complicated dry methods.