pH, alkalinity and kH...what are they??!

[Xhilr8]

Can somebody help me out here... I have a problem with my tank where I cannot seem to raise the pH above 7.8 no matter how much buffer I put in or how many water changes I do.. The lady at the LFS did a test on my water and said the water was too hard (I assume she was referring to the KH or carbonate hardness). Correct me if I'm wrong, but does kH and alkalinity refer to the same thing (generally speaking)?

And if alkalinity or kH is high, does it mean that it will be difficult for the pH to FALL as well as INCREASE? I thought that if kH/alkalinity is high, it means that pH just wont fall but you can increase it if desired by using buffers.... although buffers do not seem to work for me.

Another lady then told me the complete opposite and said that my water is probably too soft and that's why pH keeps falling to 7.8 (but it dones't really "fall" since I can't even change that pH value to begin with!). I'm getting a kH test kit coming in soon so maybe I can figure out what's happening there..

Some clarity on this would be great.

 

[steve-s]

Can somebody help me out here... I have a problem with my tank where I cannot seem to raise the pH above 7.8 no matter how much buffer I put in or how many water changes I do.. The lady at the LFS did a test on my water and said the water was too hard (I assume she was referring to the KH or carbonate hardness). Correct me if I'm wrong, but does kH and alkalinity refer to the same thing (generally speaking)?

Water hardness (often expressed in GH) basically means it has more minerals in it. Primarily Magnesium and Calcium. In a SW environment, the GH is not relavent and the two must be measured seperately to guage the balance against the KH or cardonate hardness often expressed in terms of DKH (Degrees of Karbonate Hardness) or mEq/l of alkalinity.

And if alkalinity or kH is high, does it mean that it will be difficult for the pH to FALL as well as INCREASE? I thought that if kH/alkalinity is high, it means that pH just wont fall but you can increase it if desired by using buffers.... although buffers do not seem to work for me.

Alkalinity is a measure of the waters ability to resist changes in pH but does not necessarily mean it can control the pH just help maintain it. The use of buffers will often raise both and a proper alkalinity (1.5-3 mEq/l NSW) will help keep pH stable.

If using a buffer to raise/maintain pH you are also greatly increasing the alkalinity at the same time depending on amounts. If alkalinity becomes too high, you will run the risk of damaging the organisms within your ecosystem as well as bottoming out the Ca due to Magnesium precipitation.

Often, the solution in these cases is environmental and not chemical. Having your LFS test your waters pH is actually futile. Once removed from the tank for any length of time, CO2/O2 affect the levels and skew the results. In cases of low pH and avg-high alk, the problem is most often poor gas exchange. Usually from a covered (sealed) tank, insufficient water flow, overstocking, overfeeding or some part of all. If this is a cycling tank, there will be constant shifts in the pH to the lower range due to the higher acid production from the higher ammonia source which utilizes much of the available O2.

pH is also effected by the time of day tested. In the earlier parts of the day
especially before lights on, the pH will tend to be naturally lower to to the algaes producing CO2 at night. Throughout the day once the lights are on, the same algaes begin to produce O2 allowing the pH to naturally rise up. The best time to test the pH is tyically middway through the photoperiod. You can test in the morning and later at night to determine this yourself. Whenever you do test the pH, always try to do it at the same time of day. That will help determine the stability of the pH.

I would suggest a small test. Remove a small cup of water from the tank and let it sit uncovered for about an hour. Test the water from the cup and then test the water from the tank and compare. If the hour old smple is much better, it is most likely something amiss with the set up.

I would also suggest posting some more detailed info about your set up. Have you purchased an alternate pH kit to see if the one you have now is faulty?

The Relationship Between Alkalinity and pH.... by Randy Holmes-Farley

Cheers
Steve

 

[Xhilr8]

Hi,

thanks for your reply. Its not poor gas exchange because I first thought that was the problem and tried increasing the air in the tank by more bubbles and it made no difference in the pH at all. I was told that it could be lack of magnesium due to precipitation from excessive alk levels. I've been dosing my tank with Seachem advantage calcium as well and I think I overdosed it and the guy at the LFS said that overdosing it will cause magnesium precipitation?? (or maybe he just said that high alk will cause magnesium percipitation)...

So with the alkalinity question...high alk means its difficult for a change in pH in both directions correct?

Yes, I've got two pH test kits and they are both fairly new (around 2 months old).
My tank is just a standard 2foot tank (20-25gal I think?), stocked with one BTA and one very small percula, 5 mushrooms and some LR, aragonite substrate in a plenium/jaubert cavity setup. All other tests (Ammonia, nitrite & nitrate) come back as zero and the tank has been setup for around 2 months now.

 

[steve-s]

Hi,

thanks for your reply. Its not poor gas exchange because I first thought that was the problem and tried increasing the air in the tank by more bubbles and it made no difference in the pH at all.

Bubblers or other "air injection" items will not really affect the O2 levels in the water, they usually just make a mess. Best way to increase gas exchange in a SW tank is to have a powerhead near the surface or pointed at the surface creating ripples. The surface aggitation is what will give you the greatest amount of gas excahnge, not bubbles. If you have a glass lid on the tank, no amount of tweeking will help much due to CO2 being trapped and O2 not being able to flow in freely.

I was told that it could be lack of magnesium due to precipitation from excessive alk levels. I've been dosing my tank with Seachem advantage calcium as well and I think I overdosed it and the guy at the LFS said that overdosing it will cause magnesium precipitation?? (or maybe he just said that high alk will cause magnesium percipitation)...

Excessively dosing buffers will indeed cause magnesium precip, Ca additions will not. If adding a buffer near or at the same time as Mg additions, you will also end up bonding the two creating magnesium carbonate which will also hamper your problem. Always make sure any additions (if tested for first) are always added several hours apart. Preferabley in the order of: buffer>> Mg >> Ca

Do you know what the 3 levels are for your tank?

If the levels are askew, it can also make things difficult. Alk and Ca should be >>balanced<< and Mg should represent 3x what the Ca level is in order to maintain the balance against the alk. It is usually much easier to correct these problems with a few good water changes using well aged SW. Until you understand the chem relationships, I would rely less on additions.

So with the alkalinity question...high alk means its difficult for a change in pH in both directions correct?

No, it only helps keep the pH from falling and promotes stability. It will not prevent it from rising.

Yes, I've got two pH test kits and they are both fairly new (around 2 months old).
My tank is just a standard 2foot tank (20-25gal I think?), stocked with one BTA and one very small percula, 5 mushrooms and some LR, aragonite substrate in a plenium/jaubert cavity setup. All other tests (Ammonia, nitrite & nitrate) come back as zero and the tank has been setup for around 2 months now.

Have you performed the test I mentioned previously, removing the water and testing an hour later?

A BTA is a 2 mo tank is for another thread . That can be looked at later.

Cheers
Steve

 

[Xhilr8]

Hi Steve,

I tried that removing of the water trick and still no go..I also got the KH test kit today. Did a test on it and kH was 200ppm (4meq/l). Calcium is low at around 280 and I will continue dosing it to increase it to 400. I looked at the Cal and Alk balace website and its a great article. Thanks!

THe problem is that Alk is high enough but pH still wont increase. I'm no longer adding in anymore buffer since that will just keep pushing up the Alk and not adjusting the pH at all.

Here's some specs on my tank:

25Gal Tank
Gravity: 1.025
Temp: 24-25deg Celcius
pH: 7.9
Water Hardness: 200ppm (4meg/l)
Fish: 1 small Percula clown ~ 1" long
Ammonia, Nitrite, Nitrate: 0

However, the low pH problem still persists and my clown fish in there hasn't been eating for the past 3 days. Anymore other suggestions?? I'm really stumped on this one... :?

 

[steve-s]

3 things,

Repreat the same test except this time leave the removed sample cup of water in the open sill of a window for the same amount of time.

Describe your tank set up in detail. Equipment, including all water movement aparatus and how they are positioned, age of set up, lid, maintenance, lighting and any additives.

What are the brand of test kits you are using

The problem is there somewhere, it just needs to be found

Cheers
Steve

 

[Xhilr8]

I actually took a cup of water and left it out in the open in my backyard for approx 2.5 hrs and there was no difference. So I don't think its an oxygen or gas exchange problem??

OK, I have an external canister filter (1200 litres p/h), a bubble wall at the back and the out flow of the water from the canister filter I havbe set it so that it ripples the surface of the water.

Lighting is with 2 x 20W fluros (1 daylight and 1 actinic). Lids are closed. I dose with seachem advantage calcium and if needed, seachem marine buffer. I also dose it with some Iodide about 2-3 times a week (I forgot to mention I have corralimorphs in there). Lights are currently off at the moment as I'm removing phosphates with a phosphate sponge (should be completed in the next 24-48hrs or so). I'm using aquarium pharaceuticals saltwater master test kit.

 

[steve-s]

Well you may or may not beleive what I'm going to tell you but here goes... (don't take this as being harse or browbeating, it's not meant to be)

I actually took a cup of water and left it out in the open in my backyard for approx 2.5 hrs and there was no difference. So I don't think its an oxygen or gas exchange problem??

I actually a more inclined to think either both test kits are faulty or possible "operator" error. It's not possible to have an alkalinity of 4 mEq/l and a pH of 7.8 in outside open air after that long.

OK, I have an external canister filter (1200 litres p/h), a bubble wall at the back and the out flow of the water from the canister filter I havbe set it so that it ripples the surface of the water.

The canister itself will not help aerate the water save for the outport rippling the water. As I said earlier, the bubbler will do nothing. It doesn't move enough water to add anything to a SW tank. As far as the GPH on the canister, it won't be as much as you think after head pressure and media are considered. Probabley closer to 190-225 GPH (370 empty and no verticle head) I would still suggest adding a PH. Something rated at about 150-200 GPH placed at the opposite end of the canister return.

Lids are closed.

If this is a glass lid, remove it. That will be a majority of your problem there. They trap alot of CO2 and supress the pH. If a lid is needed, replace it with eggcrate material.

I dose with seachem advantage calcium and if needed, seachem marine buffer. I also dose it with some Iodide about 2-3 times a week (I forgot to mention I have corralimorphs in there).

Unless you have scleractinians, I would skip the dosing completely and just rely on weekly water changes. Mabye twice weekly until your chem is back into ionic balance. Shrooms will not utilize anything your adding.

Lights are currently off at the moment as I'm removing phosphates with a phosphate sponge (should be completed in the next 24-48hrs or so). I'm using aquarium pharaceuticals saltwater master test kit.

Lights don't need to be off for a PO4 sponge to be effective. Without the light, you will also have less natural O2 production in the tank which will supress the pH further.

Not too sure on the Aqua Pharm test kits. Never used them so hopefully someone else may chime in on that.

All in all I would still suggest the problem is environmetal and not chemical. With an open top or replaced with eggcrate, the added PH and leaving the window in the tank room open. You should see a dramatic change in about 3-5 days providing the water changes are done.

Good Luck
Cheers
Steve

 

[Xhilr8]

Bubble wall is there for aesthetics. I had a power head in there earlier and had no effect. The return flow onthe canister is actually quite strong in rippling the water surface. Its storng enough that if the water level drops a little, the water will actually break the surface and spray in my face

Lights are off only temporarily to stop diatom algae from growing until the phosphate removal procedure is completed. I'm aware that lights do not need to be off for the phosphate sponge to work

I've tested the pH with 3 test kits so I don't think its a problem with the test kit. All test kits were new too. Aquarium pharmaceuticals test kits are alot easier to read than some of the other ones I've tried.

I dont see what taking off the lid is going to do because I've already tried that oxygen test taking a cup of water out and leaving it outdoors in fresh air...but I'll give it a shot (though I don't think it will do anything).

And yes, the kH readings are correct. I tested it twice to make sure...that's why I am so stumped on this because its quite rare to have high Alk but low pH.

Do you think its better to do the water changes with Spring water??

 

[steve-s]

Do you think its better to do the water changes with Spring water??

If you do not have access to proper RO water, it may be better than tap. I would try for the RO is possible. Tap water can often have many things you cannot test for unless your local water dept has a website listing the analysis.

Cheers
Steve

 

[Xhilr8]

Hi,

I dont have access to a RO unit and dont want to spend so much for one. Keep in mind that I have another 4foot tank that dones't have pH problems. THe only difference between the two tanks is that one uses crushed coral as substrate and the 2foot tank that has pH problems is using a marine aragonite substrate. Some guy at the LFS reckons that marine aragonite dones't really help buffer the water at all and recommended that I switch over to crushed coral..

Anyone has any input if crushed coral is better than marine aragonite??

 

[Xhilr8]

Oops, accidentely double posted. Sorry