How do I lower Alkalinity?

[cincyjim]

I apologize if this is somewhere but I searched and couldn't find anything on this.

75g, 70lbs live rock, 120lbs live sand, 20g sump, and skimmer

My Alkalinity is at 15, PH is 8.2, Ammonia 0, Nitrites 0, Nitrates 10. I've seen where the recommendation for Alkalinity to be 7-11. So, how do I lower it or do I just wait it out?

 

[jimsplace]

Check the stickys on the Chemistry forum for Randy's Chemistry and the Aquarium article, it is probably the best article I have ever seen for keeping alk/calc numbers in line. 15 is pretty high and needs to come down, but is not at the critical level. Are you dosing something which has pushed it that high i.e. something to raise your ph? If so quit dosing it and it will fall on it's own. Bring the value down slowly though.

 

[cincyjim]

I use a PH Buffer (Seachem) when my PH gets down to 7.8 - 8.0 to raise it back up to 8.2 - 8.4. Should I not be doing that? Thanks for recommendation, I'll go find that now.

 

[Chris27]

Water changes will lower it, as well as growing corals and coraline algae. Don't do it too quickly though if you have a tank full of coral....it's better to let calcification take care of it for you.

 

[stevek480]

You should get your Alk in line and maintain it in range, and then you don't need to worry about PH swings. 7.8 is at the bottom of the range but it is not too low. One thing that has a great effect on PH is how much CO2 you have in your house. In winter or when the windows are closed, PH will drop. I find when I open a window near the tank PH shoots up. There are good articles on PH and Alk in the Reef Chemistry forum.

 

[disc1]

Yessir, ditch the pH buffer, stop thinking in terms of pH and start thinking in terms of alkalinity. The pH has such a minimal effect if any on your tanks inhabitants, while alkalinity is vital.

 

[cincyjim]

Ok, this is really confusing to me...PH and Alkalinity. I did find some good articles on the two in the Reef Chemistry forum but I really didn't grasp what it was telling me.

So, if I stop using the PH buffer, are we saying then, the Alkalinity will fall naturally in place? How far do I let the PH drop before I become worried?

 

[aleonn]

If your livestock are looking OK, I'd let the high alk level dissipate naturally. You can also do water changes as well.

Besides keeping a nearby window open to allow gas exchange, you can also: 1) ensure you have good surface agitation of the water (you can point a powerhead pointed upwards to ripple the water); 2) run your skimmer 24/7, and if necessary, run a hose line near the window which further helps oxygenate the water; 3) grow macro-algae in the sump, lighted at a reverse daylight schedule in order to stabilize pH at night.

 

[Sk8r]

Here's the deal: alkalinity, calcium, and magnesium are locked in a relationship. TO RAISE ALK OR CAL: first raise mg to at least 1200. Then dose alk buffer to preferred level. Wait 8 hours. (or more) [getting it there may take a couple of doses over a couple of days.) THen dose calcium. Same story. NEver dose alk and cal within 8 hours of each OTHER.
To LOWER any of these, just wait for the mg level to fall below 1200---this happens naturally as corals and fish use it up. Once it drops below 1200, the other two begin to fall naturally.
You don't have to understand the chemistry down to the electrons---just memorize the numbers in my sig line and get your chemistry there and it will hold good. Once you have mg high, you should NOT go on adding buffer, because it raises the alk too high. Remember it can't fall until the mg gets used up. That's why you're experiencing high alk. Your salt mix has mg in it (and buffer, and calcium) and you went on dosing buffer into a system that has mg enough to hold the buffer up.

PS: I don't track ph at all. Just alk, cal, mg.

 

[disc1]

How far do I let the PH drop before I become worried?

To put it real bluntly, if your rocks start dissolving, then worry that it is too low. If there are daily snowstorms in your tank, then worry that it may be too high. If neither of these thing is happening, then pH is OK.

 

[cincyjim]

Thanks for the explanations and help on this. I don't know why but this is one area that I just struggle to grasp everytime I have to deal with it.

 

[Sk8r]

Basically your ph kind of tracks your alkalinity. It varies hour to hour in some tanks. PH will make you crazy. Alkalinity rides firm once you get the balance right---putting kalk in your topoff water is one way to lock the alk-cal-mg thing in for weeks without having to dose---though when it gets 'off' you have to start dosing again and get it set before the kalk will do what it does. I haven't checked my ph in about 6 months, but I can pretty well tell you it's what's in my sig line. How do I know? Because if it weren't the other readings would be screwed---but because the other readings AREN'T screwed, there's nothing going to mess up the ph too much.

 

[Voodoodauley]

I find this fascinating. I am trying to relate ph as it pertains to the human body. A ph of 7.4 is perfect for the human body. It can range normally from 7.35 to 7.45. When a person has lung problems they can develop respiratory acidosis in which their ph is chronically around 7.30. When a person hyperventilates their ph increased over 7.45. This is what is referred to as becoming more alkalitic. So an increase in ph is alkalosis and drop in ph is acidosis. Funny because in the fish world it is measured separately. in humans the acid and the alkaline is one and the same.

 

[disc1]

in humans the acid and the alkaline is one and the same.

No, it isn't. The medical people have just learned to track one using the other because the human body has a wonderfully evolved mechanism for balancing both. Tank water does not.

Alkalinity is a measure of the number of total basic groups in the water. That is, to be technical, the number of molecules per liter that have a negative charge or lone pair of electrons that is willing to accept a proton.

pH is a measure of the number of hydronium ions, we think of them as protons, in a sample of water.

In the tank, all of the alkalinity comes from either carbonate or bicarbonate. A small amount comes from borate, and a tiny tiny amount from other things. Since these molecules constitute a buffer system, their total concentration (what we call alkalinity) gives you a measure of the resistance to pH changes. You have to take more drastic action to change the pH of a solution the higher it's alkalinity is. That's why I liken chasing pH with a buffer to a drug addict. The more you do it, the higher your alk gets, and the more you have to add each time to get the same result. Eventually, you get into real trouble.

pH is just a measure of how many free protons are in the water. Acidity. It is a logarithmic scale, and over the range of 7.6 to 8.6 there is a ten fold difference. But over the entire range of pH, that isn't very much at all. The ends of the scale are pretty much the points where rock begins to dissolve (around 7.3 to 7.6 depending on alk and cal and mag) and the point where calcium carbonate can't stay in solution anymore (8.5 to 9.5 depending again on cal alk and mag).

As far as the animals in your tank are concerned, anything in that range, and even pretty far outside of it, is tolerable. Even on the reef in nature the pH swings every day, and with the currents and weather the swings can get pretty drastic. They, just like us, have evolved ways to regulate the pH in their tissues. What isn't tolerable is big rapid changes, and the alkalinity fights that.

 

[disc1]

One of the additional benefits of dosing your alkalinity with calcium hydroxide (kalkwasser) if you have low pH is that you are adding the alkalinity as hydroxide instead of carbonate. The buffer system in the tank has to absorb this hydroxide, and that pushes the buffer equilibrium to maintain a higher pH. In a tank with high pH, this same effect can create snow-storms.

 

[Sk8r]

And just as an fyi, you can buy kalk powder as Mrs Wages' Pickling Lime, in a grocery, or sometimes at your lfs. Using it in your topoff is sometimes referred to as 'dripping kalk'. It comes in at a ph of 12, which rapidly adjusts downward. I use it, and run my top off from a 1/4 inch tube to be sure I have a long slow adding of kalk-containing-water (kalkwasser, German for limewater) instead of a big glop of it hitting my sump all at once.

There is somewhat more to using kalk, which should be done only when you have stony coral, and when it is starting to open up and eat---a lot of calcium. It is the cheapest, safest way to dose a tank around 50 gallons, and somewhat larger. Fish-onlies and softie tanks don't use enough calcium to make it adviseable: they 'sip' at calcium, using only enough for bone and muscle. Stony coral 'gulps' calcium bigtime, because it is constantly building massive reef structure. So do what's appropriate for your kind of tank. If you need more info on kalk, I have some more info in my blog, which you can get to by poking the blue number under my avatar.

 

[Voodoodauley]

In the tank, all of the alkalinity comes from either carbonate or bicarbonate. A small amount comes from borate, and a tiny tiny amount from other things.

What a wonderful post! Thank you! The body uses bicarbonate to balance ph as well. I did not realize that marine water worked that way too. This explains a lot to me and really helps my understanding of how this all works. I can see how CO2 dosing can change the tank chemistry now too.

 

[rcypert]

Just a heads up ph buffer and alkalinity buffer are nearly the same thing. One is sodium carbonate (PH buffer) and the other is sodium bicarbonate (Alk buffer) and a lot of buffers have both. And over a period of time it all does the same thing. That is why reefers don't test their ph. If you are taking care of your alkalinity your ph is also being buffered. As stated above do not worry about your ph unless you are using a calcium reactor just open a window in the room twice a week to get some fresh air. Buffering means you are adding elements that prevent it from changing. It is a little confusing and I just added my opinion. I am not a chemist and all I know is what Randy Holmes-Farley has taught me. He has done an invaluable service to us all in this hobby. We all owe him a debt of gratitude for without him our understanding of the chemistry side of the hobby would just not be where it is. Thanks Randy! I have said it before and I'll say it again you're the man!

 

[Mark9]

I'm thinking he's got his kh down after 5 years.

 

[BeachVacationer]

So, how do I bring my kh down?