RODI Water PH very low

[lrs183]

Hello!

So I booted up my rodi system today and let it run for an hour. TDS meter coming into DI canister registers 12, then going out of the DI shows 0. With that said I used my saltwater api test kit on it to see the PH and it registered the lowest reading, if not lower. However no salt etc had been mixed in yet, this was just a direct sample from the clean water hose.

I have seachem aquavitro 8.4 pH and the calcium formulas as the dosings I run twice a week in the tank.

I also have red sea coral pro salt as my salt mix for my rodi water

My question is, based on what I have (or don't have) how can I raise the PH of the basic rodi water or rodi mixed saltwater before putting it in the tank?

Thanks you in advance :)

[dirtycontour]

RO/DI should have a pH of about 7.

[lrs183]

Based on what it looked like that sounds spot on. But I wouldn't want to add it that way to the tank right? Or am I missing a detail here.

[GroktheCube]

Based on what it looked like that sounds spot on. But I wouldn't want to add it that way to the tank right? Or am I missing a detail here.

Pure water will always have a pH somewhere around 7, depending on dissolved gas levels. This is because it entirely lacks buffering chemicals like alkalinity. None of those buffers evaporate, so using it as top off will have no impact on tank pH. Salt mix has lots of buffers, so it makes no difference there either. As long as your RO/DI is pure, the pH is irrelevant.

[lrs183]

Ok awesome, simple enough :) is there anything in particular that I should test for in the water before I start using it? Ie deadly chemicals. Or will the rodi take care of anything?

[disc1]

RO/DI should have a pH of about 7.

Pure water will always have a pH somewhere around 7

Ultra pure water will almost never have a pH of 7. It will almost always be lower than that due to CO2 entering the water. Truly degassed ultra-pure water held under an inert atmosphere with no CO2 at exactly 24.87 degrees Celsius THEN you can expect to find a pH of 7.

[disc1]

I bet this will surprise a lot of folks. pH 7 isn't always neutral.

Pure water at 24.87C has a dissociation constant of 10^-14. That means at any given time you'll find 10^-7 H+ and 10^-7OH- floating around in a liter of water and everything is balanced and neutral and happy. And the pH is 7.

But what if the water is at 50C? Then the Kw is 13.2. So at the neutral happy point, the H+ is at 10^-6.6M (and so is the OH-). That means that at 50C, neutral pH is 6.6 and pH 7 is basic.

At 99C neutral pH is more like 6.15 and something with a pH of 6.5 is actually basic.

At 1C neutral pH is 7.45 and anything with a pH of 7 would actually be acidic.

[disc1]

Ok awesome, simple enough :) is there anything in particular that I should test for in the water before I start using it? Ie deadly chemicals. Or will the rodi take care of anything?

If you're coming through RODI and reading a TDS of 0 then there's not much more you can ask for.

[lrs183]

If I could trust that my camera would take accurate photos of the vial I would show it. But it was pretty low. Lower than the 7.2 min on api. So I should be ok on everything? As unfortunately a lot of those numbers went over my head. Still new to this :/

[lrs183]

If you're coming through RODI and reading a TDS of 0 then there's not much more you can ask for.

Thank you very much!

[OceanNut]

Heat your RO/DI water to the same temp as your tank then mix your salt. Allow your pump to break the surface tension of your mixed water to allow for oxygen and carbon dioxide equilibrium. Two-three hours is good. Measure pH and buffer as necessary to match tank pH. Baking soda or a commercial buffer can be used to raise pH. Ph does fluctuate so try to do the above at the same time of day consistently.

[disc1]

If I could trust that my camera would take accurate photos of the vial I would show it. But it was pretty low. Lower than the 7.2 min on api. So I should be ok on everything? As unfortunately a lot of those numbers went over my head. Still new to this :/

You don't need to understand all that. It's just a fun quirk of the pH scale that most folks aren't aware of.


If you want to see it explained better:
http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Aqueous_Solutions/The_pH_Scale/Temperature_Dependent_of_the_pH_of_pure_Water

[disc1]

Heat your RO/DI water to the same temp as your tank then mix your salt.

Another fun chemistry fact. That crud that precipitates out of the salt mix all over the container is calcium carbonate. Calcium carbonate is really hard to dissolve, and that's why it crashes out. There is sodium carbonate and calcium chloride in the salt mix and when the two meet in high concentration the calcium and carbonate get together and fall out.

So the name of the game in mixing water is to increase the solubility of calcium carbonate. And most folks would guess that to do that you heat the water.

Actually it is the opposite. Calcium carbonate is actually more soluble in colder water. So it is best to mix your salt in while the water is cold and then heat it up. That will help a lot with the crud in the bottom of the mixing barrel.

[OceanNut]

Another fun chemistry fact. That crud that precipitates out of the salt mix all over the container is calcium carbonate. Calcium carbonate is really hard to dissolve, and that's why it crashes out. There is sodium carbonate and calcium chloride in the salt mix and when the two meet in high concentration the calcium and carbonate get together and fall out.

So the name of the game in mixing water is to increase the solubility of calcium carbonate. And most folks would guess that to do that you heat the water.

Actually it is the opposite. Calcium carbonate is actually more soluble in colder water. So it is best to mix your salt in while the water is cold and then heat it up. That will help a lot with the crud in the bottom of the mixing barrel.


For the hobby reefer we are trying to match tank pH to newly mixed water to add to the tank. My advice will work for that. I doubt we need to get into SN1 and E2 chemistry mechanisms.

[disc1]

For the hobby reefer we are trying to match tank pH to newly mixed water to add to the tank. My advice will work for that. I doubt we need to get into SN1 and E2 chemistry mechanisms.

Those are organic mechanisms. I'm talking about solubility. You'll end up with whatever pH either way, but if you want to lessen the crud and keep the alk up in your mixed water mix it cold.

[lrs183]

From posts I read a couple days ago here in RC one of the posters from red sea was taking questions and did say that mixing the salt at lower temps was the way to do it to increase success with dissolving things.

And when you say a pump in the bucket to churn it for a few hours.. do you mean just a regular power head or what?

[lrs183]

Would my aquavitro 8.4 buffer be ok to use?

[disc1]

From posts I read a couple days ago here in RC one of the posters from red sea was taking questions and did say that mixing the salt at lower temps was the way to do it to increase success with dissolving things.

And when you say a pump in the bucket to churn it for a few hours.. do you mean just a regular power head or what?

Yes, just a regular powerhead. Anything to keep it stirring especially at the surface.

[disc1]

Would my aquavitro 8.4 buffer be ok to use?

It will work as an alkalinity supplement if you find that you are low on alkalinity, but it is an awfully expensive way to go about that.

You can get more bang for way less buck by using regular baking soda from the grocery store. If you want it to boost your pH, you bake it first. Otherwise you just dissolve it in RODI and dose it to the tank.

[lrs183]

Well my tank is pretty small so I'm hopefully not gonna burn up too much stuff. 21g in total. But to bring the water from rodi up to pH of the tank. Or like said as the second post on here is raising the saltwater and fresh water from the rodi not necessary?

I'm sorry for the dumb questions.. I pretty much need my hand held through this. I'm not interested in crashing my tank right as its about to get truly fun to own.

So really I guess what in looking for is

Steps to take with fresh water from rodi to tank
.
Steps with red sea coral pro salt mix into rodi water then into the tank.

Variable is the pH of the rodi water

[OceanNut]

Those are organic mechanisms. I'm talking about solubility. You'll end up with whatever pH either way, but if you want to lessen the crud and keep the alk up in your mixed water mix it cold.


I mix my new saltwater at 77f just like the temp in my tank and have no precipitates. I need to add a half table spoon of buffer(to 10 gal.) to get the same pH and alk as my tank, 8.2/11 respectively. Do you have insight on this?

[Coral Dilema]

You used your API saltwater PH kit to measure the ph of water with no salt in it . . I wouldn't trust it regardless of what it says.

[disc1]

I mix my new saltwater at 77f just like the temp in my tank and have no precipitates. I need to add a half table spoon of buffer(to 10 gal.) to get the same pH and alk as my tank, 8.2/11 respectively. Do you have insight on this?

Yes. Yours doesn't precipitate. You have no problem. Keep doing what you're doing.

If you want less precip, mix colder. You already have none. What more insight do you need?

[GroktheCube]

Well my tank is pretty small so I'm hopefully not gonna burn up too much stuff. 21g in total. But to bring the water from rodi up to pH of the tank. Or like said as the second post on here is raising the saltwater and fresh water from the rodi not necessary?

I'm sorry for the dumb questions.. I pretty much need my hand held through this. I'm not interested in crashing my tank right as its about to get truly fun to own.

So really I guess what in looking for is

Steps to take with fresh water from rodi to tank

As evaporation top off? None, assuming water is 0 TDS.

Steps with red sea coral pro salt mix into rodi water then into the tank.

Put mixing pump in water. Slowly add appropriate amount of salt (for RSCP, I find slowly shaking it into the water works well). Once salt is dissolved, heat to appropriate temperature.

Variable is the pH of the rodi water

Assuming the post-DI TDS is 0, ignore the pH of the ro/di water.

[lrs183]

Coral dilemma I agree. I made sure to include that in the op so it was known

[lrs183]

As evaporation top off? None, assuming water is 0 TDS.



Put mixing pump in water. Slowly add appropriate amount of salt (for RSCP, I find slowly shaking it into the water works well). Once salt is dissolved, heat to appropriate temperature.



Assuming the post-DI TDS is 0, ignore the pH of the ro/di water.

So like you said earlier even for the saltwater mix for water changes I don't need to do anything?

[GroktheCube]

So like you said earlier even for the saltwater mix for water changes I don't need to do anything?

The only thing I'd really suggest checking for the RO/DI is that post-DI TDS remains 0. Assuming post-DI TDS is 0, you can be 99.9+ sure that the water is perfectly fine to use.

If you want to check the pH of anything, it'd be the salt water after you mix it up. If it is too low, it may need to be aerated more, or CO2 levels inside your house may just be a bit high. Generally speaking, I think most of the gurus here don't really advocate spending too much energy checking pH. Usually, if alkalinity is where it should be, pH will be as well.

[lrs183]

Hm ok, sounds good. Like I said I just don't want to crash my tank. I'd be pretty upset :/

[OceanNut]

Yes. Yours doesn't precipitate. You have no problem. Keep doing what you're doing.

If you want less precip, mix colder. You already have none. What more insight do you need?

Insight I am look for is...... if I mix at 77f and get no precip then can I mix at 67f and my pH and alk rise? Thus, eliminating the need to use buffer?

[disc1]

Insight I am look for is...... if I mix at 77f and get no precip then can I mix at 67f and my pH and alk rise? Thus, eliminating the need to use buffer?

If there's no precipitation now, then I don't see how the alkalinity would rise unless you add something to it. No matter what temperature you mix at, you'll mix to the same alkalinity unless you precipitate some out.

[OceanNut]

If there's no precipitation now, then I don't see how the alkalinity would rise unless you add something to it. No matter what temperature you mix at, you'll mix to the same alkalinity unless you precipitate some out.


Cool. Thanks!

[lrs183]

Yes thank you everyone for helping on this thread. If anyone else has input on stuff I should do for adding fresh and saltwater, I'll gladly hear it. If not, I'll go with grokthecube's advice!

Thank you!

[tmz]

For the hobby reefer we are trying to match tank pH to newly mixed water to add to the tank. My advice will work for that. I doubt we need to get into SN1 and E2 chemistry mechanisms.

It will work if you heat it before mixing but not as well if you mix it in cool water .If you are making small water changes room temp water should be fine and fine tuning the pH won't matter much at all since CO2 will enter the game and even things out . If the salt mix used is reasonably close to tank levels for calcium and alk ;there is no need to adjust those in newly mixed water either. The pH of 0 tds ro/di water before mixing doesn't matter at all. I wouldn't even test it.

This is the chemistry forum and we can learn from David on that score.
Understanding how things work is helpful and part of the fun.

[lrs183]

I'd say I will be doing 4 gallon (roughly 20%) every 2 weeks. Am I alright with cooler water when mixing? I may even just do 2 gallons each week.

Speaking of temperatures... is straight rodi water while its still really cold bad to mix with? Should I let it at least go room temp?

[tmz]

I'd preheat to tank temperature for a 20% change. I do 1% changes per day ;some times as high as 5% so it's not an issue for me.
Yes , cooler water has more room to hold alk and calcium in solution. So it dissolves easier. Mine is usually around 71 degrees ;my aquaium is usually at 77/78.
When you raise the temperature some may precipitate out ,the chance of that occurrig is grater as the gap in temperatures increases. . If the ro/di is very cold I'd let it rise to room temperature before mixing to avoid precipitation as it warms up or is heated. I store ro/di in a heated basement .Out water comes from Lake Erie which is really cold at this time of year.

[lrs183]

Ok, I will preheat it then. I thought about doing 10% per week to make mixing easier. Does it still need a few hours of aging time at that low of water volume?

I'm assuming you use a different heater for the water mixing? Wife is gonna kill me getting another power head and heater, haha

[tmz]

Let's try this:

Store the ro/di water you need until it reaches room temperature,say it's 70 degrees.

Mix in the salt and provide some water movement . Let it mix for at least 3 hours Longer is a plus for most salts;some like Red Sewa Coral Pro require shorter times. Yes it needs to age. I leve mine overnight.

Say your tank is at 80 degrees. The a 10% change with 70 degree water will drop the tank temp by only one degree. A 20% change by 2 degrees and so on. The tank heater will warm a small temperature drop over the course of a few hours or less and the animals in the tank can handle that variation which won't last long.

[lrs183]

Sounds good! Simple and easy enough.

My final two questions would be.. I have read in replies here to make sure the surface is getting agitated. So if in a 5 gallon bucket I have a power head facing the opposite side while agitating the top, will that be enough for mixing purposes? Or do I need a way to have one blast directly down too?

And my final question... mixed rodi water and fresh rodi water straight in the tank? Don't worry about testing anything?

Sorry for beating a dead horse. But it needed to be beaten one more time! :deadhorse:

[tmz]

One small powerhead is enough to mix it and store/age it. Just so there is some water movement.
To hurry mixing along hand stirring doesn't hurt . Adding the salt to the fresh water slowly helps it dissolve faster with less chance of preciptitaion . Say1/2 and another 1/2 an hour later.

Salt mixes need time to process amines and other elements ;many also contain added organics to help bind free metals I'd personally consider 3 hours a minimum aging period. The organics shouldn't be left in stagnant water for very long so just keep the powerhead going continuously.

Tom

No need to measure anything for ro/di other than post di tds which should be zero.

[lrs183]

I don't need to hurry it, I just didn't know if it was necessary for a small 5 gallon or less amount to age for a long time. I've invested too much already to be hasteful with mixing.

Thank you very much! I definitely appreciate it

[tmz]

You are welcome
Good luck

[lrs183]

Not to revive a finished thread, but I do have a question that came to mind tonight.

Would it be wise to maybe make a small 1 gallon batch per day/every other day and start using it in the tank to avoid any major parameter swings as pose to doing an outright 4gallon change in one sitting?

Red sea coral pro going into a LFS water filled tank btw

[tmz]

I do small water changes.,1% per day.from a 20 gallon bin of mixed /aged saltwater that I keep on hand in a 20 gallon bin with a power head ,replenishing ro/di water and salt as I use it . It's easier for me this way and there is less risk of shocking the system if something is off in the newly mixed water vs the tank water.

[lrs183]

Are the water changes as effective doing it that way? In the long run

[GroktheCube]

That's part of why I switched to ESV B ionic salt. It is totally dissolved in minutes, and has nearly identical basic parameters to my system.

Many people find a salt with parameters very close to their tank, that way large WCs with minimal instability are possible.

[lrs183]

I've heard of that salt a number of times. I guess the hope would be that in time, I can have my tank more adjusted to RCP and then do bigger changes. But like with any salt I've read my share of bad posts about RCP. Though I noticed they're almost all pre 2013 as I think they had a different formula.

Hopefully its good

[GroktheCube]

Keep in mind that even a 20% WC will only result in fairly minor swings even with fairly large differences.

It's only when you see monumental differences or perform a very large WC that you're likely to have trouble.

[lrs183]

You think so? And what's your take on siphoning the sand bed? How often and how much at a time? I don't feel like nuking my tank in that respect either.

[GroktheCube]

If you do a 20% WC, and the new water is 12 dKH, and your tank is 8 dKH, you will still be below 9 dKH after the WC.

IMHO, it is wise to vacuum the sand, unless you want detritus to build up in it. Every story I've read about a sandbed crashing a tank is because of excess crap built up in it. Usually, when someone goes a couple years without touching the sandbed, starts having nutrienr related algae problems, and then releases some nastiness into the water when they attempt to clean it. This leads some people to suggest not cleaning it is wise. Personally, I've never heard of a sandbed that was kept clean throughout a tank's life causing a crash or any other problems. I can't really think of a good reason not to clean it.

[tmz]

Are the water changes as effective doing it that way? In the long run

Been doing it this way for many years. It is a bit less efficient in removing nutrient than large changes but that's not why I do water changes. My primary reason is to keep ionic balances and add major, minor and trace elements consistent. Smaller more requent changes ar better in that respect.

[lrs183]

Well I think in the beginning I will do smaller water changes. Then gradually increase to water changes. As well should I only siphon a small portion of the sand at a time?

[bertoni]

Siphoning a bit at a time likely is the safest approach.