Some advice regarding Ph

Hi everyone,

Okay ... bit a long story but I'll try to be as brief as I can so I don't bore you all....

The tap water in my area is very very soft (Kh and Gh pretty much zero) and so my tank Ph is very low. It was because of this that I chose to keep the fish I have (I'll post a list at the end). I didn't want to add chemicals to alter the Ph and I'm not able to go RO because I live in a first floor flat, and I have health problems which mean I can't lift. I wanted to keep things simple so I could have fish without too much strenuous work.

My Ph is settled and it's reads at between 5.5 and 6 - depending on which test kit I use -API masterkit says 6, JBL kit says around 5.5. I've took that to mean it's between the two.

If I draw some water straight from my tap and test it it reads between 7.2 and 7.6 (seems to vary between the two a little). Because there is a fairly large gap between tank and tap I keep my water changes smaller (I change 42 litres a week on a 240 litre tank and stay heavily planted to keep nitrate low). I also have high readings of Phosphate (around 1. from the tap which has caused an imbalance which resulted in black beard algae and so keeping the water changes smaller and running a phosphate remover in the filter I can keep that under control.

Recently I found one of neon tetra's was looking a little pale in colour and had some marks to one side of it's body and so I made the mistake of posting about it on another forum. Naturally I was asked for my water parameters and so I gave them (Ph 5.5ish, Ammonia 0, nitrite 0, nitrate 40) within a few hours I was imbroiled in an arguement I didn't want to have about how I was making my stock sick with a Ph so low.
The neon in question was cured with two salt water baths (no salt was added to the tank - I netted it out and bathed it in a seperate jug) and now I believe it had possibly been fighting.

Now I've been left feeling like my fish keeping confidence has been completely squashed and doubting my knowledge of 4 years of successful keeping and breeding of my fish and I'm wondering if I've got this completely wrong.

All my stock are Amazonian - all soft water loving fish. I have

2 angelfish
2 laetacara curvicep cichlids
7 black neons
10 nematobrycon palmeri tetras
4 purple, gold headed harlequins (dying off from old age now and struggling to find some more)
8 peppered cories, 6 panda's, 5 bronze and 3 melini
2 ancistrus catfish and 3 oto's


So, have I got this wrong. Am I a bad fish keeper and am I killing my fish slowly? Please be gentle with me I've really taken a confidence battering and have spent the last two days bursting into tears. Thanks in advance - Akasha

The idea of a neon tetra dying, or being made sick, by a low pH is faintly ridiculous; they naturally live in water of very low pH & hardness, I've seen figures as low as 4 quoted for breeding.

You are lucky to have water that's naturally so soft, but you are treading a very fine line :-

There is a direct relationship between the kH (carbonate hardness), CO2 (carbon dioxide) levels and the pH.

For any given level of CO2, reducing the kH by 90% will result in a fall in the pH of 1 degree.

So to take an example :-  kH 10, ph7 drop the kH by 9 and the readings would be kH 1, pH 6.
A kH of 10DH (DH = German Hardness 1 DH = 17.8 ppm) would be quite high, more typical values might be 4 or 5 DH and you state that your levels are near zero, so much lower than that. The issue is that the bacteria that break down the fish waste and produce the nitrates that you're relying on your plants to remove, also produce acids in the process, these acids react with & remove the kH from the water, causing the pH to fall over time. to some extent the plants will also use some of the calcium carbonate, also causing the kH levels to drop. Typically this isn't a problem, and for an average tank, not overfed, a weekly 10% water change with tap water having a kH of 4 or 5 DH is sufficient to replenish the carbonate hardness that's been lost, and keep things stable.
Unfortunately, if you're not able to replenish the kH through water changes, there is a severe danger of pH crash. The reason for this, is that the rate the carbonate hardness is being used up is fairly constant, which means, if it takes 10 days to drop from 1.0 to 0.1, with a corresponding fall in pH from 7 to 6, it will take about 24 hours to drop to 0.01 and a pH of 5, and an hour or so later the pH will be down to 4.

So my advice to you would be, at the very least get yourself a good liquid (dip strips tend not to be too accurate) kH test kit, and monitor the kH of both your tank & your tap water, and if necessary, you will need to find some way of raising the kH. Personally I'd use a kH buffer, but if you feel uncomfortable with this, simply adding some calcium rich rocks or gravel to the aquarium would probably do the trick (something like tufa or "ocean rock") then if you monitor the tank kH, you can always remove the rock if the kH appears to be rising too high.

Providing the kH is 2DH of above, the pH should stay fairly stable, a level of 1DH is Ok provided the fishkeeper monitors it every few days, much lower than that and things can go wrong very quickly.

thank you for your reply and for being gentle.

I have a Kh drop test (it's the API one) and the last Kh test read at 2 - two drops changes the colour. That was a test I did a while ago but I was led to believe that meant it was virtually non-existent - wondering now if that was the wrong information. Everytime I check my Ph it's always the same so it doesn't appear to fluctuate until I do my water change and then it raises a little because of the tap-tank difference.

I have added some crushed coral to my filter in a filter bag but it's done nothing to raise the Ph and I admit to not checking the Kh recently. I'm losing light now and it's not an easy test to do under electric light conditions but I'll check it tomorrow morning and let you know.
Is the crushed coral the same as the ocean rock you mention? I'd rather not add chemicals and would rather go down the natural route where possible. The only time I add chemicals is if the fish have an illness that can't be cured any other way - like when I had Hexamita and had to treat them all.

You've now re-instated my confidence a little that I've chosen the right fish for the water I have so thank you


Ps - Science is one of my worst subjects so it's a good idea to keep it simple and if I don't understand I'll let you know. I do add liquid Co2 (easycarbo) ... it used to be daily but lately I keep forgetting

okay, I've just done the Kh test and the tank is Kh 1 (one drop turns the water yellow) so I repeated the test with some water straight from the tap and that is Kh 2 (1 drop it turns blue, 2 drops it turns yellow)

That said the tank is due a water change which I'm aiming to do today and so I'll re-test the Kh after the water change has been done and see if it's made a difference


It's looks like the crushed coral is doing nothing at all and is sitting in my filter for no reason. I've got two choices - add some more and see if that helps or remove it all together

I've just done the Kh test and the tank is Kh 1 (one drop turns the water yellow)

That means it's between 0 and 1, it could be 0.1 or 0.9 which makes a big difference. If you double the amount of water in the test tube, then each drop = 0.5 DH if necessary triple the amount then each drop = 1/3rd DH.

It's looks like the crushed coral is doing nothing at all and is sitting in my filter for no reason

It won't just dissolve over night, but it will help buffer the hardness. To give you an idea of the numbers, 1DH = 17.8ppm (parts per million, this is the same as milligrams per litre.) so if you have a kH of 1 in a 200 litre tank, you've got 200 x 17.8 = 3560 mg = 3.56 grams of calcium carbonate in your entire tank, equivalent to about 1/2 a teaspoon of crushed coral. Try putting a couple of teaspoons of crushed coral in a jam jar of tap water & monitor the kH over a couple of weeks, you'll see the kH rise, but the higher it gets, the more slowly it rises..

hello again, not had chance to digest your reply but I thought I'd give you the update first.

I've just changed my usual 7 buckets of water (each bucket holds close to 6 litres so it's about 40/42 litres) Before I added the clean water I drew off 5ml from the bucket and put it in a test tube and set it aside while I added the water. Once the tank was filled back up and the filters were running again I added some Ph regent to the test tube .... Ph7. So according to my new JBL test kit my tap water (dechlorinated - not sure if that makes any difference though) is neutral.

I let the tank settle for a few minutes and drew off 10ml from the tank and tested both the Ph and the Kh with the JBL kit (my API kit is old now and I wondered if the brand new kit would offer a different reading)

The tank Ph has raised from 5.5 to 6.5 so not so bad for the fish? Common sense says they'll cope with that but you may disagree.
Now the Kh test confused me. The process is the same as API ... add the regent one drop at a time and count the drops and watch for the water turning from blue to orange.... So one drop and the water stayed clear ... 2 drops and still clear ... 3 drops and finally it's changing colour to a pale orange. What the heck does that mean?

As I've said I'm useless at Science related stuff ... I spent too much time bunking off at school (I hated school as was never academic) and so when it comes to chemistry I just can't understand it... my brain just doesn't seem to work that way. Sorry, I'm sounding really thick


Forgot to say the coral has been in my filter nearly a year and there's a large handful in. I have some more but it's in a large piece that I'd need to try and smash up. Should I add some more? There may be room in my second filter

The tank Ph has raised from 5.5 to 6.5 so not so bad for the fish?

since you said :-

I'm useless at Science related stuff ... I spent too much time bunking off at school (I hated school as was never academic) and so when it comes to chemistry I just can't understand it..

you're not going to like my reply :-

pH is on a log scale* so a change of 1 in the pH, actually represents a ten fold change in the acidity, so quite a shock for the fish. It probably won't kill them, but swings like that are best avoided.

* log scale the numbers 10, 100, 1000 & 10000 can be written as 10 to the power of 1, 2, 3 or 4 respectively; ie 10 with a little number to the top right of it - I don't know how do that on forum! so 100 is 10 x 10 ie 10 to the power of 2; 1000 10 x 10 x 10 is 10 to the power of 3. the pH scale is equivalent to 2 or the 3 in this example

the fact that your pH went up from 5.5 to 6.5 shows that you've raised the carbonate hardness ten-fold.
The accuracy and reliability of test kits does vary from brand to brand, but unless the instructions say otherwise, that would suggest a kH of 3. which would suggest that the kH has risen from 0.3 to 3.
Your tank is 240 litres, so allowing for gravel you've changed roughly 20%. That would suggest your tap water has a kH of about 15. That would be quite a high reading. In practice the accuracy of test kits is limited by your ability to judge colours, measure quantities, variability in drop size, and the ability of the manufactures to print their colour comparison cards accurately. In short, these are guides rather than 100% precise. But it does suggest that you would benefit from doing some more frequent water changes for a while, to help raise the kH to a more stable point.

Forgot to say the coral has been in my filter nearly a year and there's a large handful

Over time the coral will form an oxide layer, which makes it hard for more calcium to dissolve. Since the coral has been in for a year, I'd remove it and crush it further to expose fresh surfaces to allow more to dissolve.

thanks for all this ... I'm starting to slowly get a better understanding of the one thing about fish keeping I've never really grasped very well - the whole chemistry side of things is the thing that has kind of gone over my head a bit...


So ... smaller changes more frequent? If it means changing a bucket every other day then I'll do it! I might actually find it easier to manage a bucket a day or every other day! (I find water changes a real struggle with my poorly joints)

So, I have a slight update since this morning. I've just returned home from a trip out to the shops which just happened to mean I was passing an lfs. I called in on the way past and they happened to have some ocean rock and a lot of it was really tiny pieces so I asked the staff member if I could have the tiny bits - after explaining why he showed me some stuff by API that you can add to the water that re-minerises it aswell as dechlorinates but after chatting about it I said I had live plants and this stuff isn't good with live plants and so that stayed on the shelf. He grabbed a fish bag and filled it with all the tiny bits of ocean rock from the bottom of the basket and said I could have it for free ... which was really appreciated.
So I now have quite a lot of ocean rock in a fish bag! Before I start cutting up a pair of old tights is there anything I need to know about ocean rock? Is it okay with my cories and ancistrus who can't tolerate salt etc?

As for the coral, I'm going to remove it and replace it with this ocean rock and give that a go. I was going to add a small handful first and keep an eye on the water ... alternatively I can add some to a glass of tap water first to see what it does ... might that actually be safer? I have no idea what I'm doing here so I'll wait for your guidance

Thanks again for all this and I'm sorry for being thick

Chemically ocean rock is pretty much the same thing as coral, so a net bag, such as an old pair of tights & put it in your filter will be fine. You might like to try putting a bit in a jam jar with some water, just so you can see what effect it's having.

So ... smaller changes more frequent? If it means changing a bucket every other day then I'll do it! I might actually find it easier to manage a bucket a day or every other day!

1. test the kH of your tap water with your new test kit.
2. test your tank water this evening, once it's had chance to settle.
3. You're aiming for a minimum kH of 2 in the tank. If it's at 2 or above, go to 6.
4. If the kH is below 2 you need to do regular, ideally daily, water changes. The more you change, the more rapidly you will get the kH up to the target level, on the other hand, change too much and the pH will swing violently and the greater the risk you'll upset both fish, and the filter bacteria. Exactly how much water you need to change will depend on your tank kH & the kH of the tap water you're using (don't assume this is constant, it will vary day by day, and more profoundly depending on time of year, and how much rain there's been recently).
I'm wary of confusing things with too much maths, but to give an example, if your tank is at 1 and your tap water is 5, if you did a 10% change then the new kH of the tank would be 0.1x5 + 0.9*1 = 1.4 Change 25% and the figures would be 0.25x5 + 0.75x1 = 2  
This really only becomes critical if your kH is very low.
5. the day after a water change test the tank kH, if it's below 2 go to 4, if it's 2 or above, go to 6
6. If the tank is at 2kH or above, just settle to doing 1 or 2, 10% (24 litre) water changes per week
7. Monitor the kH each week if the kH drops below 2, go to 4.

thanks ... I think I've understood all of that. The only problem I can see is doing a Kh test now this evening in poor electric light. I'll try in a moment but I suspect it'll be impossible to read with energy saver light bulbs.

I'll test the tap water and tank again in the morning though when light is at it's best and post up the results. The rock is still in the bag at the moment. I've had a disaster with my dog and had to rush her to the vet and so now I'm looking after a dog that can't walk aswell as the tank! Fun and games ... not

morning! I have some results and some photo's for you.

The JBL kit agrees with the API regarding the tap Kh. It also says Kh-2. The tank is still Kh-1

I retested the tank Ph aswell and I just wanted to show you what I'm dealing with in regard to reading what the Ph is.

This is the colour card


And this is the test bottle



It's anyone's guess whether it's 5, 5.5 or 6. There's no wonder I'm confused and I have to say I won't be getting another of these kits

I'd say 6 rather than 5.
Do you have a second water sample bottle? If so, assuming you use 5ml for a test, put 5ml of water from the tank in one, and do the test in the second, now place the test chart on a flat surface, and put the pot with 5ml of tank water on top of one of the coloured circles, and your pot with the tank water on the adjacent white circle, looking down on the two, you should find it much easier to compare the colours.

With a kH of 1, I'd carry on doing 10-20% water changes daily, or every other day, and see if you can get the kH, & therefore the pH, up a bit.

Hi again. The kit tells you to do it the way you've suggested so I'll give it a try in the morning - again, electric light now so reading it accurately is impossible now.

So an update. I've taken some of the ocean rock (about a handful) and washed it under the tap and I've got it in an old stocking ready to go into one of the filters tomorrow.
The rest of the rock has also had a rinse and is in a bucket half filled with water from the tap. I'm going to leave it in the bucket of water over night and check the Kh of it in the morning - just to see if it's done anything. I checked the Kh when it went in and it's still at 2 so no change in the tap level. I'm not expecting much difference by morning but I just want to check I'm not going to get a swing when I add it to the filter.

I was aiming to change 1 bucket of water today but time has run away and it's not got done yet. There's still time this evening though.
I'm really worried about shocking the fish though and so if possible I want to try and take this slowly - unless you tell me differently.

I have another option though that I want to run past you... Some time ago I did an experiment with my water. I got 3 clean glasses - in 1 I just put clean dechlorinated water, in the 2nd I got a handful of my old pea gravel, washed it well in running water and added it the glass with water. In the 3rd I added a handful of sand from the tank (washing that well too) and left all three glasses to stand un-covered for 5 days. I tested the Ph (but not the Kh - kicking myself now) daily. The plain glass didn't fall by much - that settled at Ph7 and stayed there. The gravel glass fell to 6.8 and stayed there but the sand glass fell drasticly to Ph6. It suggested to me that there might be something in my sand that's affecting the Ph (and potentially the Kh too).
So the other option might be to start swapping my sand out for the old pea gravel. If I went down this route I'd do it very slowly. Because my aquascape is a pathway scape I'd look to replace the centre part first - sucking out the sand bit by bit.

It's one heck of a task and it's not something I relish the thought of but if it might help the Ph and Kh it could be worth it. What are your thoughts?

update:

I re-tested the tank Ph how you suggested Pterophyllum and it is indeed Ph-6. As for the bucket containing the ocean rock .. well that is Ph-7.5 and Kh 2-3 (2 drops and it was mostly clear, 3 drops and it was the obvious yellow so that would look like the rock in the bottom has moved the Kh by a very small amount.

However - Ph-7.5 is too high for my stock in my opinion and so now I'm stressing that I'm going to go from one extreem to the other by messing about.

And of course, as if to make matters even more difficult and stressful my angels are planning a spawn. They are obcessively cleaning a leaf which is less than 2 inches from the top water level and the female is gradually lowering her breeding tube ... this is going to make it virtually impossible to water change daily without disturbing them .... why can't it ever be easy!!

A pH of 7.5 is fine, but then 6.0 is too, the problem comes if the pH crashes to 5 or even 4, it's just 6 is more likely to crash than 7.5. Personally I'd say somewhere close to 7 is ideal. If you don't want to add Ocean rock to the tank, leave some soaking in a bucket of water until you're ready to do a water change, and then use that water for the water change. If you monitor your tank pH & KH regularly, you'll be able to trim the pH/KH to your target, by adding more or less "ocean rock water" depending on your readings.

I told my Dad all about this this morning and he said the same - use the water that the ocean rock is in to top up my tank a jug at a time! Dad's been a fish keeper all my life so he's got 40+ years of fish keeping experience behind him

I still plan to put some of this rock in my filter but at the moment I'm trying to figure out how much to add. I want to see how the bucket changes first - it should give me very rough indication of what it will do once added to the tank. In the meantime I'm keeping an eye on the tank - the Ph has been at 6 for the entire year and a half that it has been running. I'm not expecting a Ph crash tomorrow but now I'm mindful of it I can watch things a bit more closely. I think (and say if you think I'm being silly) a week of the rock in a bucket and daily Ph and Kh testing will give me an indication of how it's going to behave once added to a filter. A week will also give the angels time to do their breeding thing (I'm expecting failure again) and then I can get to grips with this Ph/Kh issue.

Thank you for all your help and I'll keep you up to date with how it all pans out

Just an update:

I tested both Ph and Kh on the bucket containing the ocean rock this morning - first time in about 3 days. I wasn't expecting anything but the Kh has moved.

Ph is still 7
Kh is now 3

So, I'm leaving things be for a few days longer and checking it some more. If it stays stable I might risk putting it in the filter.


The only thing that's making me stall is my cories. Common sense says it's ocean rock ... there has to be some salt in there somewhere ... the cories can't cope with salt and I love my cories dearly and I can't risk harming them

Despite the name, I'm not convinced that ocean rock is actually extracted from the ocean. On the other hand crushed coral, which you had in the filter previously, certainly did originate under the sea.
Whilst Cories are sensitive to salt, the small amount that you might introduce with a small amount of rock wouldn't bother them, especially if you rinse or pre-soak it as you have done.

okay ... thanks. I'll carry on with the bucket a little longer and if it stays stable at Kh3 then I'll take the risk. The coral has been in the filter over a year and the cories are fine so you've convinced me I'm worrying over nothing

Thanks again

Quick update now that the bucket has had a week with the rock in

Kh in the bucket is still at 3 and Ph is still at 7 and so it would seem it's now stable.

I've got my phosphate remover to change out this weekend -which means opening a filter - and so I'll add the rock at the same time and then keep an eye on the tank and post what happens

Thanks for all the help

Just here to say I added some of the ocean rock to my filter today - I couldn't get it all in though but that might be for the best. I'll check my water stats tomorrow and see how things are looking.

If there's no change I'll see if the remainder of this rock will fit in my other filter. I'll keep you posted

Ok, I'm sure all will be fine

I have been following this on and off, I did attempt to post a reply about the x10 difference in pH values, but thought I might be trying to 'teach my grandmother how to suck eggs' and I have only very basic knowledge of Kh

I like the approach of putting water in jars, adding stuff and testing because all of that really builds understanding. Questioning what is in the tank and how is it changing the water, all good in my opinion. These posts will be read in the future when my brain is ready to tackle water chemistry 101

the 'jar test' was only really to see if the sand was changing anything and the test proved it was. There's other things within the tank though that could be altering Ph ... things like bogwood which is known to soften water and lower Ph. I have lots of bogwood in my tank and I guess that is playing a part too.

I've not tested my water yet as we've had a stressful few hours and I'm being delicate with the tank today. Last night my two male ancistrus decided to try and kill each other after nearly 3 years of living peacefully together. In the process they ripped my tank apart - plants were torn up and decor over turned. The rest of my fish were terrified and hiding where ever they could find. I've only just dared to turn the lights on but I can tell they are still jumpy.

One of the ancistrus went to live in my Dad's tank last night - it was obvious that these two couldn't live together anymore. The remaining ancistrus has just come out prowling for food and the fish - cories especially - just scattered. If this doesn't improve he may have to go to my lfs to be re-homed.

So today, I'm just leaving the tank alone and allowing everyone to calm down. I've tip-toed up to it and thrown some food in and tip-toed away. I'm still incredibly stressed myself so I dread to think how they must be feeling! I've never seen anything like that and I'm used to warring cichlids!

Yes, practically everything you put in your tank will alter the water chemistry because water is able to dissolve so many things. Thankfully it doesn't dissolve glass, otherwise we'd have to keep buying new tanks.

The ancistrus might have behaved like that anyway but it could also be a response to changing environmental conditions.

Less bogwood in your tank would slow down the ability of the bogwood to lower the Ph. It looks nice and yes it lowers the Ph, but it will continue to lower the Ph of low Ph water, in other words it doesn't know when to stop!

You won't know if the fish are jumpy in relation to the ancistrus incident or changing environmental conditions, so keep an eye on the water parameters, gently, gently...