# Ro Water Ph



## Chris25 (11 Jun 2019)

Hi all,

I'm trying to breed some cardinal tetras and to do so have a small 20 litre tank with a small sponge filter, heater set at 26c and 6 cardinals in.

I believe to breed cardinals I need to get the ph to between 5.5-6.0.

My tap water ph comes out at around 8.5 and is hard. To lower the ph in the water I was initially using HMA water and had some peat in the bottom of the tank which lowered it to around 7.8. To lower it more I added quite a few alder cones which again bought it down slowly over a few days but only to around 7.2. 
So to get it lower I did a water change of around 80% with RO water which was 6.0. But now after a couple days the Ph has gone up to 8.0 again. The fish seem fine, as I know quick Ph swings aren't good for them and can be fatal.

I don't know what I'm doing wrong...

What can I do to lower the ph of my water and keep it consistent at 5.5-6.0. I don't want to use any chemicals to do this.

I can do some water tests again tonight if you need more specific numbers.

Thanks,
Chris


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## dw1305 (11 Jun 2019)

Hi all,





Chris25 said:


> and 6 cardinals in


You need to try and <"just select a pair">, they are serial egg eaters, even the spawning pair will eat the eggs as fast as they lay them.

If you can get mosquito larvae they will condition the fish like nothing else.  





Chris25 said:


> So to get it lower I did a water change of around 80% with RO water which was 6.0. But now after a couple days the Ph has gone up to 8.0 again.


 It is because of the carbonate ~ CO2 ~ pH equilibrium. Water which has any degree of carbonate buffering (dKH) will return to ~pH8.  This is how a drop checker works, you change the pH equilibrium point by adding more CO2.

Do you have a conductivity meter? I find them more useful than a pH meter at low levels of hardness, I'd aim for less than 50microS (~30 ppm TDS), which  may well be about 95:05 RO and Tap.  





Chris25 said:


> The fish seem fine, as I know quick Ph swings aren't good for them and can be fatal.


The problem is with pH as a measurement, it is the negative log10 ratio of the activity of H+ ion acceptors (bases) and donors (acids). As you get towards pure H2O pH becomes less and less meaningful or stable.

I look at changes in pH in terms of changes in water chemistry, if a large change in pH reflects a small change in water chemistry you can ignore it. It is back to the reason why you can lower the pH with added CO2, without pH changes troubling your fish. 





Chris25 said:


> What can I do to lower the ph of my water and keep it consistent at 5.5-6.0. I don't want to use any chemicals to do this.


Just add plenty of Oak leaves and Alder cones to the 95% RO water. You want the water to be black tea coloured.





Chris25 said:


> had some peat in the bottom of the tank


Peat is good as a substrate, I like a big wodge of moss as well and a fairly well aged sponge.

The water tint will help with the egg development, and I always add a floater to the breeding tank.

cheers Darrel


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## Chris25 (11 Jun 2019)

Hi Darrel,

Thank you so much for the reply.

The reason I went with 6 is because I'm not 100% sure I can sex them correctly. I think there are 3 pairs but I could be wrong. I'll try to get some pictures of the 6 and I could remove 4 and keep a pair. They are a little over a year old.

I've been conditioning them on live brine shrimp with occasional live bloodworm for the past couple of weeks in this tank as I can get that easily from my LFS, I didn't notice mosquito larvae but will have a look.



dw1305 said:


> Do you have a conductivity meter?


I have a TDS meter, is that what you mean?
The water I put in had a TDS of 0ppm. I'm not sure on what the reading is now. I can do another when I get home from work.
It's an RODI unit I'm using and I've replaced all the filters and DI resin and flushed it through before getting the water for the 80% change.

Am I right in thinking, the Ph is always going to go back up to around 8, but it's the TDS that I need to keep down which makes the water softer?
Then by adding the alder cones this brings the ph down. I can't lower the ph just with the RO unit?
Would I be best to fill a bucket with the RODI water, add a load of alder cones and an air stone and the use this to do the water change after its aged for a few days and the ph has dropped. More cones = quicker and further drop?



dw1305 said:


> I like a big wodge of moss as well


I have got a lot of java moss which I added, I put a lot in and then it started floating around the tank and I couldn't see anything so I took some out and left a clump.
Along with the tank going a very dark brown colour from the alder cones it was impossible to see anything. 
How will I be able to tell if they've laid eggs and I should remove them, if I can't see in? I believe the eggs are photosensitive so shining a strong torch in wouldn't be a good idea?



dw1305 said:


> I always add a floater to the breeding tank


I don't have any floating plants, there's no light on the tank. Should I get a couple of floating plants and a light?

I'll get a picture of my setup tonight.

Thanks for your help and sorry about all the questions,
Chris


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## dw1305 (11 Jun 2019)

Hi all,





Chris25 said:


> I'm not 100% sure I can sex them correctly.


Look at them from above (best) or the side, a big wide (from above) one is a female. 





Chris25 said:


> I didn't notice mosquito larvae but will have a look.


It is the right time of year to "grow your own", it is incredibly easy, you just need a builders buckets a handful of grass cuttings (or similar) and a cork (or similar).  Have a look at <"live food cultures">. I mainly feed the fish live food and I don't buy any from April to October. 





Chris25 said:


> I have a TDS meter, is that what you mean?


Yes, they are all really conductivity meters, they just use a conversion factor (0.64) to convert microS to  ppm TDS, so 100 microS is 64ppm TDS.  The Rio Negro would have single figure conductivity values. 





Chris25 said:


> Am I right in thinking, the Ph is always going to go back up to around 8, but it's the TDS that I need to keep down which makes the water softer? Then by adding the alder cones this brings the ph down. I can't lower the ph just with the RO unit?


Yes sort of, pH is basically meaningless in DI water. The conductivity (TDS) value doesn't tell you anything about pH but if it is a really low value you don't have many ions of any description. 

If you have no dKH the water will read ~ pH 5.8 just because of the small amount of dissolved CO2. As soon as you add any bases (H+ ion acceptors) then the water will go up to pH8. When you add Alder cones (or Oak leaves) they contain humic compounds (that are H+ ion donors) and the pH will fall. 


Chris25 said:


> I have got a lot of java moss which I added, I put a lot in and then it started floating around the tank and I couldn't see anything so I took some out and left a clump. Along with the tank going a very dark brown colour from the alder cones it was impossible to see anything.


Perfect, that is exactly what you want. If the pair is conditioned you can just assume they have spawned over night and take them out in the morning, you should be able to see that the female is much slimmer. 





Chris25 said:


> I believe the eggs are photosensitive so shining a strong torch in wouldn't be a good idea?


They are, but you can. 





Chris25 said:


> I don't have any floating plants, there's no light on the tank. Should I get a couple of floating plants and a light?


No don't get them specially, I always have a range of floating plants so I can just scoop one or two in. They aren't essential for this. 

cheers Darrel


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## Chris25 (12 Jun 2019)

Hi Darrel,

I took a picture of the 6 and I've put what I think are the males and females and am just wondering if you can check? The females have a taller body as well when looking from the side.



 

I've just checked the water and ph is 7.9 and TDS is 260 now, will the substrate increase the TDS as it was 0 for 80% of the water added. 260 is what comes out of the tap. Surely if 20% of it was at 260 and 80% at 0 it should now be diluted to around 52? (260/5)

Can I throw in a load more alder cones to bring the Ph down quicker?



dw1305 said:


> If the pair is conditioned


How do I know they are conditioned and ready to spawn? Will they not spawn with a ph much over 6.0?

I'm guessing they could have spawned (if they will in a high ph) and I've not seen it, so can't now just take them out in the morning and assume they have? Unless they spawn daily?!

Thanks for all your help,
Chris


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## dw1305 (12 Jun 2019)

Hi all, 





Chris25 said:


> I took a picture of the 6 and I've put what I think are the males and females and am just wondering if you can check? The females have a taller body as well when looking from the side.


Yes that was how I would sex them, the females look well conditioned. 





Chris25 said:


> I've just checked the water and ph is 7.9 and TDS is 260 now, will the substrate increase the TDS as it was 0 for 80% of the water added. 260 is what comes out of the tap. Surely if 20% of it was at 260 and 80% at 0 it should now be diluted to around 52? (260/5)


It should be ~50 ppm TDS.

It may be the peat has exchanged all its H+ ions for Ca++ ions (in the hard water) and is now exchanging Ca++ ions for H+ ions. Calcium (Ca++) ions are more strongly bound than hydrogen (H+) ions, but cation exchange depends on both the <"lyotropic series and the concentration of ions in solution">.   Also the peat needs to be <"sphagnum peat">. 





Chris25 said:


> Can I throw in a load more alder cones to bring the Ph down quicker?


You can, I'd get rid of the peat you've and possibly just go for moss and alder cones? I might be tempted to start with 100% RO and just add a tiny dash of tap water.





Chris25 said:


> how do I know they are conditioned and ready to spawn? Will they not spawn with a ph much over 6.0?


The females will just get fatter, after they've spawned they will slim down again. I've not kept Cardinal Tetras for a long time, but most Tetras spawn quite freely when conditioned, even in "unsuitable" water for the eggs to hatch. 





Chris25 said:


> Unless they spawn daily?!


Usually about 14 days until a female is ready to spawn again.

I kept Black-Neon Tetra (varying amount, but up to about 15), as dithers, with _Apistogramma cacatuoides,_ and in the summer (with plenty of live food) the Tetras would spawn every couple of days and quite a few fry would make it big enough to avoid being eaten.

cheers Darrel


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## Chris25 (13 Jun 2019)

Thank you so much Darrel for taking the time to help.

I'm going to go with your suggestion and strip the tank down at the weekend and fill with RO water and add a tiny amount of HMA water. Should I add HMA water until I hit TDS close to 50ppm or should I aim lower as it may rise again?
I'll add a ton of java moss as a layer at the bottom and have no substrate. The stuff I have in there at the moment is the co-co fibre brick stuff, usually used for reptiles, I watched a youtube video which said to use this.

I'm thinking I'll remove all but one of the females. I'll keep feeding her live food and then in a week or so when she looks plump, add a male and then remove them the morning after. (Assuming the water stays at a low ph and low TDS value). 
Does the male need conditioning as well, as I'd have to put him back in the main display tank as I don't have another setup available. They get fed a decent diet but it's not live food. Frozen and a mixture of dried foods. I'm going to start a couple of cultures of mosquito larvae at the weekend so will look to start using that when it's ready.
Will the female keep hold of the eggs until a male is put with her or will she release them when she's ready anyway? 

Would you say any of the females in the picture look like they are carrying eggs at the moment? I'm not sure how rounded they'd go?

Thanks,
Chris


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## dw1305 (13 Jun 2019)

Hi all,





Chris25 said:


> Does the male need conditioning as well,


He does but not to the same degree as the female. 


Chris25 said:


> hey get fed a decent diet but it's not live food. Frozen and a mixture of dried foods. I'm going to start a couple of cultures of mosquito larvae at the weekend so will look to start using that when it's ready.


You can condition fish with frozen food, I've always used live food because I always have it available.





Chris25 said:


> Will the female keep hold of the eggs until a male is put with her or will she release them when she's ready anyway?


Wait for the male in most species. 





Chris25 said:


> Would you say any of the females in the picture look like they are carrying eggs at the moment? I'm not sure how rounded they'd go?


Yes they look about right, they can get bigger.





Chris25 said:


> The stuff I have in there at the moment is the co-co fibre brick stuff, usually used for reptiles, I watched a youtube video which said to use this.


Should be all right, put some in a beaker of DI water and see if the conductivity rises overnight. 





Chris25 said:


> Should I add HMA water until I hit TDS close to 50ppm or should I aim lower as it may rise again?


Start lower, you can always add things, taking them away is the difficult bit.

cheers Darrel


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## Chris25 (17 Jun 2019)

Hi Darrel,

So on Saturday I emptied the breeding tank, put 5 fish back into the display tank and kept one female (the roundest).



 

I removed all the substrate and put a layer of Java moss over the bottom and half filled the tank with RODI water. (TDS 2ppm, 5.8ph)
I've got a 25 litre bucket with RODI water in and an air filter for future water changes. I've been testing this too. Should I add alder cones to this to bring the ph right down? (I'm starting to run out of alder cones...)
I also kept a bit of the substrate and put some in a jar with the RODI water.

I've taken multiple readings since.

*15/06 23:25*
Tank - TDS *37*ppm, PH *6.9*
RODI - TDS *2*ppm, PH *6.8* (Gone up)
Test Jar - TDS *31*ppm, PH *6.4*

*16/06 12:00*
Tank - TDS *37*ppm, PH *7.2* (Added a load more alder cones to try and bring this down)
RODI - TDS *2*ppm, PH *6.9* (Up again...) 
Test Jar - TDS *40*ppm, PH *6.5*

*16/06 20:45*
Tank - TDS *53*ppm, PH *6.8* (alder cones seem to have made a slight difference lowering the ph, would these also have caused the TDS to go up?)
RODI - TDS *2*ppm, PH *7.3* (Up again...) 
Test Jar - TDS *48*ppm, PH *6.8*

*17/06 18:00*
Tank - TDS *56*ppm, PH *6.8* (Do I need more alder cones to bring it down further? I can't see into the tank it's so dark now) KH less than 1 so why isn't this dropping quickly?)
RODI - TDS *2*ppm, PH *8.0* (Up again, I've just tested the KH of the water and it's less than one, (API test did expire, 01/19), so why is it returning to 8? I tested my main display tank and that was a dKh of 17 / 304.3ppm.) 
Test Jar - TDS *59*ppm, PH *6.8
*
It appears the substrate I had initially didn't make a huge difference to the parameters.

I don't see how I can get the ph down anywhere near 5.5-6. When I add alder cones the TDS goes up. It just seems impossible... I've tried reading about KH which seems to suggest if that's very low the ph will swing really easily.
I'm more confused than ever!

Thanks,
Chris


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## dw1305 (17 Jun 2019)

Hi all,





Chris25 said:


> When I add alder cones the TDS goes up. It just seems impossible... I've tried reading about KH which seems to suggest if that's very low the ph will swing really easily.
> I'm more confused than ever!


It is just that pH isn't a very useful measurement as you approach pure H2O. 





Chris25 said:


> Tank - TDS *53*ppm, PH *6.8* (alder cones seem to have made a slight difference lowering the ph, would these also have caused the TDS to go up?)


Any soluble salts, that go into solution as ions, will cause a rise the TDS. 





Chris25 said:


> I can't see into the tank it's so dark now


Perfect, just ignore the pH. 





Chris25 said:


> I don't see how I can get the ph down anywhere near 5.5-6.


A drop of white vinegar would do.

cheers Darrel


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## Chris25 (18 Jun 2019)

Thanks for this Darrel, I'll add the white vinegar tonight and see how I get on!

Thanks,
Chris


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## Chris25 (4 Feb 2020)

Hi Darrel,

It's been a long time but thought I'd update you on my breeding success! I've managed to get a few baby cardinals!
I'm now using rainwater on the tank and that seems to have done the trick!

I haven't removed the parents so think that is why I'm getting so few come through. I'm going to separate the males from the females and then re-introduce after a couple of weeks and see if I can get a good batch!

Thanks again for all your help!

Chris


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## dw1305 (4 Feb 2020)

Hi all, 





Chris25 said:


> It's been a long time but thought I'd update you on my breeding success! I've managed to get a few baby cardinals! I'm now using rainwater on the tank and that seems to have done the trick!


That is brilliant, not many people successfully spawn any of the "Black water" Tetras. 

I've got a _Copella_ sp. <"spawning at the moment">, but none of the eggs have developed, possibly because the water (~130 micro S.) is still too hard.

cheers Darrel


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## Witcher (6 Feb 2020)

dw1305 said:


> Water which has any degree of carbonate buffering (dKH) will return to ~pH8



Hey Darrell, can this process be stopped (or slowed down) using buffers similar to the ones used for calibration, or is it rather asking for troubles due to the amounts of ingredients needed (especially for phosphate buffers)?


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## dw1305 (6 Feb 2020)

Hi all, 





Witcher said:


> Hey Darrell, can this process be stopped (or slowed down) using buffers similar to the ones used for calibration, or is it rather asking for troubles due to the amounts of ingredients needed (especially for phosphate buffers)?


Yes, you can adjust pH to any given value, using pH buffers, but I don't think it offers any advantage. The problem is that as you add salts the conductivity of the water rises, and you end up with "salty" water with a low pH, which is significantly different from naturally soft water with low conductivity and low pH.

I quite like the "tea analogy" for this, if you start with boiling water and add a tea bag, you have a bitter solution, "black tea"  you can add milk and sugar to it to remove the bitterness etc. "white tea" but as you've added things you've moved further and further away from the original boiling water.

Carbonate buffering is a bit like making tea, but in this case natural processes have added CaCO3 (dGH/dKH) to rain-water and you can only get back to rain-water by removing them via an RO unit etc. Adding more things just isn't going to work.

The other issue is that if you start with really hard water you need to add a lot of acids to counter act the amount of bases. In terms of removing carbonate hardness, you can reduce the conductivity gain to some degree by using hydrochloric acid (HCl), (because that converts some of the CO3 to CO2, which is out-gassed), but you still have the extra chloride Cl- ions.

The <"usual buffers people use"> are either sodium citrate - citric acid (weak base - weak acid) or phosphate buffers. Sodium phosphate is cheapest but <"Gomori buffers">, di-potassium/potassium hydrogen phosphate would be more suitable for a planted tank, if you really wanted to go down the buffer route.

*Drop checker*
I should have clarified the drop-checker bit as well. When people add CO2 to their tanks  the drop checker is actually making use of the CO2 ~HCO3- ~ CO3  buffer system. In that case you have a known about of carbonate (the base) in the 4 dKH solution and a variable amount of CO2 (the acid) added. You can estimate the CO2 addition from the change in pH, indicated by the <"colour change"> (protonation state) of a narrow range pH indicator (bromothymol blue).

cheers Darrel


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## Witcher (6 Feb 2020)

@dw1305 thanks for the links with recipes, I'll definitely try them, even for the sake of experimenting. I keep my tank with very soft water (approx 2 dGH/dKH but pH swings are rather large and in the area of 7.5-8 pH) so hopefully amount of salts needed for the buffering won't be large.


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## dw1305 (6 Feb 2020)

Hi all, 





Witcher said:


> I keep my tank with very soft water (approx 2 dGH/dKH but pH swings are rather large and in the area of 7.5-8 pH)


You can just ignore the pH swings in soft water, they occur in any vegetated water just due to the changes in the oxygen/CO2 ratio during the photo-period. Have a look at <"TDS and remineralising...">.

The problem is really with pH as a measurement. Because it is both a ratio and a log^10 scale it always needs some interpretation, and the real problem is that two similar pH readings can mean very different things in water chemistry terms.

With all these sort of "chemistry" things, as a general rule of thumb, I just think about them in terms of changes in water chemistry, if something doesn't cause a rapid large change in water chemistry I just don't worry about it.

cheers Darrel
.


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