Aquarium Chemistry Question? Ask the Doctor!

[Jason0203]

You have a few different options for Alkalinity and Calcium but most of them involve some kind of dosing. Other than more frequent water changes the only non-dosing option I am aware of is using a calcium reactor.

pH in a reef tank has two main components. Alkalinity and CO2 content of the water. If you maintain your alkalinity around 8dkh it will give you a little pH boost. Otherwise, running an airline from your skimmer to outside can help with pH if you feel it is a problem. Adding a CO2 scrubber to your skimmer air intake is another option.

I have some Kalkwasser that came with the tank, but I don’t have the reactor for it. I read you can dose it with your RODI water but that is more focusing on the calcium with a side effect of Alk and PH. Would that be a better option than getting a 2 part additive?

 

[Brew12]

I have some Kalkwasser that came with the tank, but I don’t have the reactor for it. I read you can dose it with your RODI water but that is more focusing on the calcium with a side effect of Alk and PH. Would that be a better option than getting a 2 part additive?

Kalkwasser is balanced between Alk and Calc and gives a temporary pH boost. You do not need a special reactor. You can add it to your top off water but I don't like that method. First, it is hard on your ATO system. Second, you can't get consistent levels because your evaporation rate won't be the same all of the time.
In my system I use dosers. I dose 1400mL of saturated Kalkwasser spread out over 70 small additions a day. I then dose 60mL of each 2-part spread out over 12 additions a day.

How much is your Alk dropping in 24 hours?

 

[Jason0203]

Kalkwasser is balanced between Alk and Calc and gives a temporary pH boost. You do not need a special reactor. You can add it to your top off water but I don't like that method. First, it is hard on your ATO system. Second, you can't get consistent levels because your evaporation rate won't be the same all of the time.
In my system I use dosers. I dose 1400mL of saturated Kalkwasser spread out over 70 small additions a day. I then dose 60mL of each 2-part spread out over 12 additions a day.

How much is your Alk dropping in 24 hours?

I have a 90 gallon DT and a 20 gallon sump and I usually do a water change of about 6 gallons each week. I did one a week ago of 20 gallons when I noted the problem and my Alk afterword was 9 a week later it is 6.5. I’m not so much worried about the PH. The tank is a year old and the PH has been 7.8 consistently since the beginning and everything in it seems to be happy. I started to notice my Hammers a little upset the last couple weeks and I am hoping this is the cause. So I can fix it.

 

[Dkeller_nc]

In general, water changes just aren't going to keep up with the carbonate (alkalinity) and calcium consumption of a reef tank with a substantial number of stony corals. Knowing that is the case, your observations are completely expected (starting at 9 dKH and dropping to 6.5 in a week).

As Brew noted, you will need to think about some sort of dosing for maintaining your calcium and alkalinity. That can take the form of using saturated kalkwasser for your top-off additions, additions of calcium chloride and sodium carbonate/bicarbonate "2-part" solutions or the output from a calcium reactor. Kalkwasser is as easy as stirring up a bunch of kalkwasser powder ("kalkwasser", by the way, is calcium oxide/hydroxide) into RODI water, allowing the undissolved material to settle out, then using the clear solution as top-off water for your tank. The downside to kalkwasser is that it just doesn't contain all that much calcium and alkalinity, so it's not possible to keep up with the tank's demand if it has a lot of corals.

That's why most people choose 2-part dosing solutions. It requires very little equipment, and is relatively inexpensive and highly effective at keeping calcium and alkalinity stable.

 

[Brew12]

In general, water changes just aren't going to keep up with the carbonate (alkalinity) and calcium consumption of a reef tank with a substantial number of stony corals. Knowing that is the case, your observations are completely expected (starting at 9 dKH and dropping to 6.5 in a week).

As Brew noted, you will need to think about some sort of dosing for maintaining your calcium and alkalinity. That can take the form of using saturated kalkwasser for your top-off additions, additions of calcium chloride and sodium carbonate/bicarbonate "2-part" solutions or the output from a calcium reactor. Kalkwasser is as easy as stirring up a bunch of kalkwasser powder ("kalkwasser", by the way, is calcium oxide/hydroxide) into RODI water, allowing the undissolved material to settle out, then using the clear solution as top-off water for your tank. The downside to kalkwasser is that it just doesn't contain all that much calcium and alkalinity, so it's not possible to keep up with the tank's demand if it has a lot of corals.

That's why most people choose 2-part dosing solutions. It requires very little equipment, and is relatively inexpensive and highly effective at keeping calcium and alkalinity stable.

+1 on this.

Here is a link to a calculator so you can determine how much of a chosen product you need to add to keep things stable.
http://reef.diesyst.com/chemcalc/chemcalc.html

 

[Jason0203]

+1 on this.

Here is a link to a calculator so you can determine how much of a chosen product you need to add to keep things stable.
http://reef.diesyst.com/chemcalc/chemcalc.html

Thank you both. I think I will start with the Kalkswasser since I already have it and then see if that will help. If not I will look into 2 part. I’m going to do another water change today and then start dosing from there. I might also try to run my skimmer air lines outside too. I live in a brick house in south Miami so air flow isn’t always the best.

 

[Millimylilly]

How fast can you safely change parameters in a tank? My ph was 7.6 so I added a little buffer which brought it to 7.7 but also raised my Alk from 10 to 10.9. I am trying to get to the recommenced ph of 8.2 but I do not want to stress the corals. Thanks for any help on this

 

[Dkeller_nc]

Do not add "pH buffer" to a reef tank! What you've observed is precisely the problem; it is not possible to add a chemical substance to seawater that will simultaneously raise the pH and not raise the alkalinity. And big alkalinity swings will be far more harmful to your corals than a "low pH". Also keep in mind that ph test kits just don't work very well in saltwater. So you really must use a pH probe if you want an accurate measure of this parameter, and it must be accurately calibrated.

Overall, the best way to affect tank pH is to ensure that you have good gas exchange (with a skimmer, for example) and that the air that's being pulled into the tank doesn't have an elevated CO2 concentration. That's quite common with newer dwellings that are tightly sealed for energy efficiency and during the winter months.

 

[Millimylilly]

Ah ok thank you for this! I will not add more buffer then. It must be the gas exchange. If it’s not a big deal I won’t mess with it!

 

[Brew12]

Do not add "pH buffer" to a reef tank! What you've observed is precisely the problem; it is not possible to add a chemical substance to seawater that will simultaneously raise the pH and not raise the alkalinity. And big alkalinity swings will be far more harmful to your corals than a "low pH". Also keep in mind that ph test kits just don't work very well in saltwater. So you really must use a pH probe if you want an accurate measure of this parameter, and it must be accurately calibrated.

Overall, the best way to affect tank pH is to ensure that you have good gas exchange (with a skimmer, for example) and that the air that's being pulled into the tank doesn't have an elevated CO2 concentration. That's quite common with newer dwellings that are tightly sealed for energy efficiency and during the winter months.

+1 on this. pH in a reef tank only has 2 significant factors. CO2 content and Alkalinity. The only way to raise pH without impacting Alkalinity is to lower the CO2 content of the water.

 

[Art2249]

Can you mix soda ash and bicarbonate to make a solution that doesn't raise ph as much or is it necessary to do one or the other. This time of year I frequently open the windows and my ph almost hit 8.4 yesterday before the lights started dimming.

This would cause the doser to shut off obviously.
Alk 8.6
ca 440
mg 1380
nitrate 4
phosphate .02

 

[Eagle_Steve]

Bump Day....

 

[Randy Holmes-Farley]

Can you mix soda ash and bicarbonate to make a solution that doesn't raise ph as much or is it necessary to do one or the other. This time of year I frequently open the windows and my ph almost hit 8.4 yesterday before the lights started dimming.

Yes, you can mix any ratio you want to control the pH effect. Mostly bicarb and some carbonate will be pH neutral, with the exact neutral ratio depending on the pH you want to have no effect on (more bicarb at lower pH).

 

[Randy Holmes-Farley]

There's also nothing wrong with hitting pH 8.4 or even pH 8.5.

For years my tank ran pH 8.35-8.55.

 

[OutsideBrian]

New to reefing, where do I want my alkalinity? Just purchased a test kit. New water /salt mix is 10 and my display is currently 7.5

 

[Dr. Dendrostein]

Thanks, Rev!

Can i use ammonia for a rash on my hand?

 

[Dr. Dendrostein]

Can i use ammonia for a rash on my hand?

Don't bug the doctor, can't you see he's busy with real patience

Sorry doc

 

[Dkeller_nc]

New to reefing, where do I want my alkalinity? Just purchased a test kit. New water /salt mix is 10 and my display is currently 7.5

Hopefully you're still monitoring this post, sorry no one picked it up. This might be better asked in the main Reef Chemistry forum, as you'll get more replies.

The answer is complicated, and depends on what you're keeping in your reef. The very short and not-enough-detail answer is:
For fish only, it really doesn't matter all that much as long as it doesn't fall so low that the pH in the tank is drastically affected.
For soft corals, like mushrooms, zoas, leathers, etc... it again doesn't matter all that much as long as you keep it above about 6.5 dKH, though you might want it a bit higher if you want coralline algae to grow in your tank.
For LPS corals, it matters more, and folks tend to keep it in the 7 -9 dKH range. Most LPS are fairly resilient, and some degree of alkalinity swing between water changes is well tolerated.
For SPS corals, especially acropora, the alkalinity really matters. Not so much the actual value, typically kept between about 8 to 9.5 dKH, but the stability of the alkalinity value. Ideally, it shouldn't vary more than about 0.5 dKH per day.

 

[Randy Holmes-Farley]

New to reefing, where do I want my alkalinity? Just purchased a test kit. New water /salt mix is 10 and my display is currently 7.5

I recommend 7-11 dKH for typical reef tanks.

 

[Jason0203]

This might be a dumb question but if I need to add 7.5ml of Alkalinity each day can I water it down with RODI water to make it 15ml so I can have my auto dose do it over the course of the day?