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Anna's Aquarium

PH issues - Feeling lost and unable to fix my tap water.

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Hello my name is Anna and this is my first post. 

I am in need of desperate advice and help with regards to maintaining a safe and stable PH in my tropical aquarium. Currently I have a 120lt tank with an assortment of tropical fish bought from our local fish store. I noticed the other day after testing my water that the PH was at 8.1, usually my tank sits at 7.6. Nothing inside my tank had changed and decided to test the tap water prior to a water change, once aerated the water from our tap tested at 8.2! I'm unsure how the tap waters PH has changed so drastically in our area but it has. 

After seeing the reading on my Aqua One Propen I freaked out a little and instantly ran to our local fish store and purchased Seachem Acid buffer to lower the PH. Over the course of the next 3/4 days I dosed my tank twice a day to reduce the Ph by 0.1 each time with the goal to achieve a PH of 7.5, by doing so I've created quite a mess for myself and am desperately seeking some advice on how to fix, get back to normal & I'm unsure if I'm hurting the fish in the process and should leave my PH alone.

My issues now

Currently I have a PH that sits around 7.5/6 during the middle of the day but constantly fluctuates throughout the day (It's a planted tank) 7.4 early morning and prior to lights out 7.7. Is this normal? Have I created these swings by using the Acid Buffer? I tested my KH and it's at 2 degrees,  I assume the acid buffer is cause for this? My hardness is 8/9 degrees.

I'm concerned that the fluctuating PH will harm my fish and I could potentially lose them, are my concerns for nothing, is this normal for all aquariums?

Secondly my biggest issues is now water changes, after lowering my PH to an unstable 7.4 - 7.6 I tried to prepare a 40lt container of buffed water to complete a water change using Seachem Acid buffer and Alkaline buffer following the guide on the Alkaline buffer bottle to achieve a 7.5.76PH. My calculation was based on 40lts as follows;

Tap water once aerated - 8.2 - Goal PH 7.5/6 = 0.6 point drop.

I used 6g of acid buffer and 15g of Alkaline buffer as directed by the ratio 1 part acid : 2.5 parts Alkaline which in theory should give me a PH of 7.6ish... As each 1g of acid buffer per 40lts drops the PH by 0.1 - as I understand it. I filled my 40lt container aerated and tested PH - 8.2, added the mixed acid buffer solution in first and then mixed the alkaline buffer  in second and waited 35mins before testing the water parameters with my Ph pen.

First test was a PH of 7.5! I was so excited that it'd at least been within the area I wanted, I let aerate for another 35mins (in the hope of stability)and tested again and the prepared water was at 8.2 again!

Please help! What am I doing wrong! Why can't I maintain a stable PH in my prepared water container? Does PH fluctuate in all aquariums naturally? If I decide that lowering and preparing water is too difficult will my tropical fish survive the 8.0+ PH!

Should I leave my tap water alone?

Currently lost and overwhelmed. 

Any advice would be nice!



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Hi Anna.

Welcome, and hopefully you can get some help.  Be aware you will likely hear different suggestions as well.

First off, don't go chasing numbers.  If you get your fish used to tap water - whatever the parameters are - then they will be fine.  Saves you work trying to adjust it all the time also.  Fish can deal with parameters outside their supposed "ideal" conditions, but they prefer stability over quick, large changes.  Let the water be what it is. 

You didn't mention your water source, but if it is Brisbane tap water, that should be fine for most fish.  I've found Brisbane water - where I am - to have a relatively stable pH around 7.8, so definitely on the high side of neutral.

Second - try to avoid adding stuff to the tank, unless absolutely necessary.  Buffers can just make your life difficult in the long run.  Yes pH changes during the day, as long as your fish are coping, I wouldn't worry too much.  If you think the pH is a little high, you're better off doing some natural modification like putting in a few chunks of driftwood (after curing, if you wish) which will tend to bring the pH down a little and also will help to stabilise the tank.  

Having said this, there are certain additives that are essential - dechlorinator to new water being the main one.

You didn't mention the types of fish you keep, just "tropicals".  Most of these are tank-bred rather than wild caught, and are quite tolerant of a range of conditions.

Good luck.



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Hello Michael and John, thank you for the tips and advice!

The fish I keep are;

- Sterbai Cory

- Redline Torpedo Barbs (Denison)

- Neon, Albino

- White fin ornate tetras

- Pygmy Cory

I assume most of these fish are hardy, with the exception of the neons?

Yes Michael I am in Brisbane, in the Kedron Brook area. I find my PH is 7.8 too from the tap but once aerated it's about 8.2+. The reason i mention aerated is because once it enters the tank, the same conversion will happen?

So, how do I go about reversing what I've done? Small water changes? How often? I assume a big water change will have a big PH swing?

Thank you again :)

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Yup, those fish are all fine, even the neons.

I wouldn't do anything, really.  Just stop adding chemicals, let the water be.  You've recently done a water change, so leave it alone until the next change.  Then, using 50/50 rainwater is a good idea as johnbetta said, that will help to lower pH and also to dilute any chemicals.

If you don't have any driftwood yet, I'd add some for stability (and aesthetics if you choose carefully).

Other than that, just let it settle.

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Thank you again Michael, no follow my annoy questions. I'm sorry!

- So once aerated my water will be above 8.0 and that's fine - Noted.

- I do have several bits of driftwood in the tank, along with Asst swords and Java moss.

- I can follow the above advice with one catch, can I purchase rain water? (We live in a top floor unit)

Kind regards,


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No worries Anna.

Don't know if you can purchase rainwater.  Might be easier to purchase an RO or an RO/DI unit and make your own.  That's if you really can't put a bucket out when it rains to catch some.

But the rainwater is not essential, just a good idea if you can get it.  I would not do more than 50% rain/RODI water though.  Even with my discus I do 50% tap water/ 50% RODI.

Probably also a good idea to monitor the pH of the tank water, but just once a day, at the same time of day.  What you're looking for is stability, rather than any specific value.


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Anna what are the kH and gH levels ?

Carbonate hardness is what stabilises the water parameters but also increases pH

the pH levels will vary in a planted tank with plants absorbing and releasing CO2

You can buy demineralised water in 4lt contains at Woolies supermarkets that you can add to 

your pre conditioning drum for water changes to reduce kH levels and drop the pH

drop a couple of containers in and test

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Hi Anna.

I'm using almond leaves at present, but I don't find it moves pH much.  Gives the water a nice colour, and won't hurt the pH, but I would not rely on this to move the pH more than 0.1 or so. Have never used peat moss.

Rainwater is pure H2O (in Australia anyway) so there are no minerals in rain water either.  And RODI similarly has all ions (minerals) removed.  Hence my saying only use 50/50 with tap water.  The demineralised water from Woolies as l2h suggests would be essentially the same as either (pure) rainwater or RODI.


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