High pH

I have just done my weekly water quality checks and all was well there.
One of my small irritating sons then requests that he would like to test some water , so armed with instructions, test kit and various warning and threats he was sent out side to test Tiddlers water ( my rogue out door axolotl larvae as opposed to my own developing larvae that has been given the same name!!). All those where fine , but the pH came back a lovely dark purple, which with this test indicated a pH of over 10. I repeated the test with the same test kit plus another and it was the same. This tank is outside and the only water ever put in is rain water, it was originally used for daphnia and other water borne beasties, this is all it contains bar some elodea . I tested the water butt water and this came back as 6.5, and this I thought should have been the same. Needless to say I am perturbed...does any one have any ideas why this should be so alkaline..I would have expected it to be far more acidic. I will do some small regular water changes with dechlorinated tap water to bring it down .




P.s am I the only one who can not use the icons within the text?......

The most common cause of this sort of pH is a chunk of concrete or lime. Check the elodea is not weighted down with anything inappropriate. Your water changes should correct things.

Icons are available to me via "go advanced" not quick reply.

I don't have too much to say about your pH, it is awfully high but I'm not sure what would be causing it. Look for things that could be leaching lime or other alkaline substances into the water. Is their clay on the bottom? Concrete blocks? Cement? I imagine it is something like this that is throwing off the pH, that or a large amount of decaying plant/animal/waste material.

As for icons, if you want them in your post click on the smilies to the right of the reply box. The icons on the bottom with the radio buttons are for the title of your post, not the inside of it. Like the question mark you have on the top of your post in the title.

Thanks for the replies, as the tank is rarely cleaned I think it will be the leaves that have blown in. I'll start cleaning these out , there aren't loads but maybe enough to trigger the problem. There's no substrate or rocks in there and the plants are free floating so that can be eliminated.


Still no luck with the icons <------ thats the best i can do!

High Ph

I should think leaves would be more likely to lower Ph than push it up to 10.

Is this exterior tank against a concrete rendered wall, or sheltered by, say, a garage with concrete roof tiles? Rain could be running over such a roof and dripping into the tank or driving against a concrete wall, or fence post, and splashing down into the tank?

Keep looking for concrete! I've just noticed a box in additional options below the reply to thread box an option labelled disable smilies in text. Is it marked with a tick? If so un-tick it.

Ho hum....very perturbed now! now concrete in tank ( no access to the demon smileys in text either..I have searched high and low!!) . The tank only contains one 2-3 cm axolotl larvae, a few sprigs of elodea...a hoard of daphnia, some small snails and a few eggs of various insects. The tank is in a shaded part of the patio sitting ( rather inconveniently) on my bench, under the kitchen window. It is approx 2 metres from the pebble dashed wall of the house and a wooden shed. When it rains/ snows etc it tends to blow onto the direction of the wall. The tank itself was covered most of the winter months with a plastic sheet and some polystyrene to protect from the worst of frost.

I have found some smiley's that I can cut and paste..my life is now compete for the moment!!

High Ph

Bang goes my theory!

Clutching at straws now, but is there a rock in the tank which could in fact be concrete. Lots of garden centre stones are not the real thing.

Has the plastic sheet been used to mix concrete on?

If not it's a fiendish plot by your pesky cats!

Definitely no secret rocks, and as I was posting earlier I seriously considered those pesky cats .They sit on the window ledge close to the tank wailing to be let in :dizzy: . After all it must be far too dark and cold for the poor little mites...but no the tank has stayed free from any thing deposited by the cats ( unlike the garden that is quietly filling with Hectors stolen treasures..a woollen duster on a stick is the latest!):lol:



Now I have found out why I had no smiley power.. I was using the most basic settings for the site!!:blob:

That is weird...
As Platinumtwo pointed out, the leaves should have lowered the pH, not hightened it.

Maybe we should start at another point - if you have no concrete and so on in your tank, could you tell us what IS in there? Do you use any kind of substrate? Any decorations?

And goes the pH up again after you changed the water?

Seeing as people are throwing around the 'concrete theory', I thought I might add that a way to test for concrete is to add a couple of drops of dilute HCl (hydrochloric acid). But keep in mind that this is only a presumptive test.

There are 2 ways you could go about this:

1. Test the base (that isn't in contact with water) of tank, and if it bubbles then it most likely means that there is concrete lining the base.

2. Test the water directly. (CAUTION: Never add water to acid). The same observations will be noted if there is concrete particles in the water.

Jay.

The tank itself is glass, there is a tiny amount of sand ( the same type as in the indoors tank) and the rest as before. Is there any possibility that it may be the daphnia that are causing this. They have been there breeding very happily since approx August and ( hangs head in shame) the tank has not really been touched at all since, barring the removal of the odd leaf.
I have done two 20% water changes since Sunday and the colour of the tester has lightened slightly. I feel I shouldn't rush this much faster as I don't want to upset Tiddler...would be a shame if anything should happen to him now.

I haven't any other straws to draw in trying to explain the pH. Just keep doing the partial water changes as you are, and it should get better. It's odd, because almost any biological activity (leaves or daphnia) are more likely to lower the pH than to raise it. Unless you have lime trees there in England

Quite the mystery indeed

I only have one other suggestion for the abnormally high pH: Atmospheric cabron dioxide. Seeing as your tank is located outside, it does make sense to hypothesise this possibility.

I'm sure you're already aware of this but there is no harm in reiteterating. All the dissolved gases in tank water (including the rare noble gas- argon) are also in present in the atmosphere. At some point in time, the amount of dissolved gases within the tank will reach an equilibrium with the atmospheric gases. As for how much gas is dissolved into the tank depends on the solubility of the gas and the temperature of the water.

Carbon dioxide, however, has the potential to be a natural buffer because it can become a bicarbonate in water. The general process of carbon dioxide is as follows:

1. Carbon dioxide from the atmosphere bonds with water water molecules (from the rain), thus forming carbonic acid. This is one of the characteristic traits of 'acid rain' which has a pH of roughly 5.7

2. In the tank, carbonic acid is rapidly deprotonated (i.e. loss of a hydrodnium ion) by the water molecules, hence forming a bicarbonate.

Bicarbonate itself is basic and it will invariably raise the pH. Therefore, it is reasonable to say that pH is the resulting balance between carbon dioxide and alkalinity, KH (a.k.a. carbonate hardness). These three (pH, carbon dioxide, KH) are always interrelated. Generally speaking, as the amount of dissolved carbon dioxide increases, as does the KH and the same with pH.

The best way to test this theory is to conduct a series of KH tests. But you have to keep in mind that the charts that are provided with the KH test kits are notorious for being incorrect. These charts can exaggerate the carbon dioxide levels by up to 20%

Anyway, that's all I can think of seeing as concrete, daphina and leaves have been ruled out...

Jay.

just a thought, it could be the sand, if the tank is unfiltered then the sand could build up the ph, and if the indoor tank is filtered then by the very process of filtering the ph will drop. try getting some rain water and testing the ph, put some of the sand in, leave it for a day, then test it again.
As i said just a thought

Thanks all

Thanks all for the suggestions.. Jay you now have me somewhat flummoxed :kiss: with the science( though unusually for me it made some sense..tired old brain has never been good with chemistry and so forth.).. it could be something to do with the gases, but I can't think of a way that I can test the theory. The window cleaners came this morning and I checked they hadn't been doing any thing with the tank..was surprised that they had noticed the resident as he is well camouflaged.

Jay, as far as I know, atmospheric carbon dioxide would increase acidity in the long run and thereby lower tank PH so I wouldn't think it would be that... I know this applies to saltwater tanks so perhaps it is not the same for freshwater and I am getting mixed up. Basically (from what I remember), the bicarbonate formed is not enough to offset the lowering of the PH that Co2 causes with the initial formation of carbonic acid.

This is probably a stupid suggestion that you have tried already bellabaloo but it was the only thing I could think of given most other things have been ruled out: do you use test tube test kits? Because recently I kept getting a reading of 9 for PH on both my test kits. I gave the tube a good scrub and then retested and it was my normal 7. So for me I had that issue as the test tube had something alkaline in it (who knows what though!) I know you tested using two different kits but did you use the same test tube? Also are the two kits of the same type and purchased around the same time? Just thought that because you've ruled out most things and it could be dodgy test kits (though two at once would be a big coincidence).

Edit: from what I have just read, CO2 lowers fresh water PH as well... but not sure about long term effects.

Saspotato said:

Jay, as far as I know, atmospheric carbon dioxide would increase acidity in the long run and thereby lower tank PH so I wouldn't think it would be that... I know this applies to saltwater tanks so perhaps it is not the same for freshwater and I am getting mixed up.

Click to expand...

If you read my post again you will see that carbon dioxide goes through a range of processes. In general the reaction of carbon dioxide with water is as follows:

carbon dioxide <-> carbonic acid (water from the rain) <-> bicarbonate (from the tank water)

<-> means equilibrium arrows. The reaction itself will favour towards the right (i.e. towards bicarbonate) because there are more water molecules in the tank and therefore, the water molecules will take a hydronium ion (H30+/H+) from the carbonic acid turning the carbonic acid into bicarbonate. The reason this happens is because a water molecule is a strongly polarised molecule due to the lone pair electrons associated with the oxygen atom.

By the way it's pH not PH

Jay.

Yes I know you explained the processes but I am not sure I agree anyway

Also it is CO2, not Co2, you missed that one of mine... and for you I would like to point out that it is Atmospheric caRBon dioxide. But meh, I hate nitpickers.

Edit: I guess on further reflection the bicarbonate created could potentially raise PH levels in a tank but not necessarily. I would suspect that most people's experience would be the opposite of how you have described, given that C02 is a recommendation in most places for lowering PH. Also a CO2 rise more likely to be a problem indoors in shut up houses than outside... But anyway as much as I love to discuss things like this I better stop going on about it

Saspotato said:

Yes I know you explained the processes but I am not sure I agree anyway

Also it is CO2, not Co2, you missed that one of mine... and for you I would like to point out that it is Atmospheric caRBon dioxide. But meh, I hate nitpickers.

Click to expand...

Sorry if that's what you I think I was doing ("nitpicking") but it's always good to give the correct information, especially when PH as you so put it, means anything but than pH.

Nonetheless, I'm interested as to why you disagree. I'm not saying that my theory is correct, which is why it's a hypothesis. But would you like to shed some light?

Jay.