RO Water and pH readings

[sonicninja]

Hi everyone,
I'll try to keep this brief as I have already posted this question on another forum with some helpful but limited feedback.

I recently had some fish deaths which I've narrowed down to the difference in pH between my RO/Tap water mix and the lower pH in the tank at around 6.5-7.0 (caused in part by my CO2 injection and the substrate/wood/almond leaves)

I do a 50-60% water chance once a week with a 50/50 Tap/RO mix and so far my pH readings for this have been very high at around 7.7. It was suggested to me that I up the ratio of RO/Tap to 70/30 to lower the KH but this has resulted in an even higher pH of 8.7.

Ive tried aeration and the addition of almond leaves to the barrel of water and if anything this has only increased the pH. Im using an electric pH pen to take readings but have also used liquid test kits (new).

If anyone has any suggestions then Id love to hear them, im very far behind on my water change but still would rather have high nitrates instead of shocking the fish with a big pH swing and risk more deaths.

I dont want to flood this initial post with too much info but please let me know if there's any other info about the tank that I should provide.

Many Thanks

Keith


50/50 RO/Tap Mix- 04/05/14
TDS 161
Ammonia 0 mg/l
Nitrite 0 mg/l
Nitrate 20mg/l
GH 140mg/l
KH 80mg/l
pH 7.7

70/30 RO/Tap-08/05/14
pH 8.7 (only reading taken as of this morning)

Pure RO Water- 04/05/14
TDS 16
Ammonia 0 mg/l
Nitrite 0 mg/l
Nitrate 6 mg/l
GH under 20 mg/l
KH 20 mg/l
PH 8

 

[ian_m]

RO water by definition should have a pH of 7, TDS of zero and GH of 0. If it hasn't you need to sort first.

Sounds like an issue with your RO. Could understand it being slightly below 7 if it absorbed CO2, but higher....Houston we have a problem...

Lots of things can cause this...
- Worn out RO membrane.
- Ruined RO membrane (usually due to chlorine and insufficient or failed carbon pre-filter).
- Failed or used up carbon pre-filter.
- Failed DI unit on output (if used).
- Defective pH meter.
- Un-calibrated pH meter.
- Contaminated pH meter.
- Contamination of RO water due to improper storage/piping.

So loads of problems.

I also doubt that pH changes will cause fish deaths. In the wild, pH changes occur all the time ie after rain etc and don't cause all the fish to die.

You are dechlorinating you water you mix with RO are you ? Lack of dechlorination will kill fish.

 

[Sacha]

Measuring pH of pure RO water is meaningless. The ionic bonds within the water are far too weak for there to be any real value.

So first of all, ignore any readings taken of pure RO.

Secondly, your readings are incorrect. It's not possible for your "RO" to have a TDS of 16, and a KH of 20 mg/l. By definition, 20 mg/l of CaCO3 will add 20 PPM of TDS to the water.

There is something wrong with your measurements. I don't know whether it's the pH pen or the hardness tests that are incorrect.

Why do you think your fish died as a result of the pH difference between your tank and tap?

 

[sonicninja]

Thanks for the informative advice. Wow, lots of things to think about. The RO unit is relatively new and probably had about 50-60 Gallons through it in total after the initial running to flush the debris out of the system. Yes, Im using a dechlorinator with every water change.

I will check my readings again tonight, would i be useful to give a full set of results for the new 70/30 mix? It maybe have been that the reading should have read 'KH under 20 mg/l' as the Hagen test kits I have don't measure accurately under that amount.

Ive been reading up as much as possible about this subject and i was under the impression that It was pretty important that you ensure the pH of the water you're adding is similar to the tank pH or you risk 'shocking' the fish. Is this an old wives tale?

 

[Sacha]

Right, in that case your KH tests are probably correct after all.

The most important two things to match are temperature and TDS. pH shock doesn't really exist in fish. What shocks them is the change in TDS, or hardness, or the relative composition of "salts" in the water.

Fish don't know what pH is. They know what magnesium, calcium, carbonate, sodium, etc are. That's what matters really.[DOUBLEPOST=1399540633][/DOUBLEPOST]In future, you should aim to match the TDS of your tank and tap as close as you can. Assuming that the water has come from the same source each time, and you match the TDS and temperature, you have nothing to worry about.

It is important the water comes from the same source though, so the composition is the same.

 

[sonicninja]

This is ace, some fantastic feedback. Much appreciated sasha. I will stop worrying about matching the pH in that case.
"In future, you should aim to match the TDS of your tank and tap as close as you can."

Excuse my ignorance on this matter concerning TDS. If im trying to match the TDS of my tank and water change water should I not be avoiding the use of an RO unit this this will reduce my TDS? This is all might confusing, I havent considered the idea of 100% RO and the use of a remineraliser either.

 

[sciencefiction]

Excuse my ignorance on this matter concerning TDS. If im trying to match the TDS of my tank and water change water should I not be avoiding the use of an RO unit this this will reduce my TDS? This is all might confusing, I havent considered the idea of 100% RO and the use of a remineraliser either.

If you want to have lets say TDS of 150ppm in your tank, then the water you should be putting regardless of the what % mix between tap and tank should also be 150-ish ppm after your mixes. Obviously with a pure RO mineralised you can aim at specific TDS, Gh and Kh as well. That's your starting point. and a newly setup tank would have this TDS.
The TDS in a tank does rise over time due to stuff naturally produced such as dissolved organics/nitrates, etc.. so it's normal to get a bit higher at the end of a week before water change but then you do a water change with a water mix of 150ppm again to bring it down. If the TDS in the tank doesn't stay 150ppm but lets say in a couple of months regardless of water changes it has risen to 250, then presuming you are not adding fertilisers accumulating, it means the bioload is a bit too much or the water changes are not often enough and big enough to keep the TDS at a certain range.

I personally am not convinced Ph changes don't affect fish, especially on the upward, but it's not exactly the value of the Ph that is harmful but which changes and chemical processes are behind it and the consequences of them in a tank to all inhabitants.
So to be on the safe side, unless you know you are intentionally altering the Ph by a certain process like the addition of CO2 or humic substances like alder cones/leaves/peat, you should aim at a stable Ph, stable TDS, etc, though either value of them doesn't speak much as it could be a number of different factors playing roles in why your tests/meters measure that particular value.

 

[dw1305]

Hi all,

I recently had some fish deaths which I've narrowed down to the difference in pH between my RO/Tap water mix and the lower pH in the tank at around 6.5-7.0 (caused in part by my CO2 injection and the substrate /wood/almond leaves).... Ive been reading up as much as possible about this subject and i was under the impression that It was pretty important that you ensure the pH of the water you're adding is similar to the tank pH or you risk 'shocking' the fish. Is this an old wives tale?

The "old wives" have struck, it is unlikely to be anything to do with pH, as the others have said pH is a fundamentally meaningless measurement in very soft water. CO2 is a much more likely killer.

Ive tried aeration

There is the suggestion that RO needs re-oxygenation, but this untrue (unless you keep a lot of RO in a sealed container with a very small surface area to volume ratio). Oxygen is a the base in O-H, and that accounts for the pH rise.

Pure RO Water- 04/05/14 - TDS 16

I'd believe the TDS meter, they don't actually measure TDS, but they measure conductivity and that is a pretty straightforward measurement. All the other tests (including your pH meter) are likely to be inaccurate.

50/50 RO/Tap Mix- 04/05/14
TDS 161
Ammonia 0 mg/l
Nitrite 0 mg/l
Nitrate 20mg/l
GH 140mg/l
KH 80mg/l
pH 7.7

You can get all the information you need from that, your tap water is fairly hard (check with your water company to get an accurate range). This means that you can just cut your RO with tap to give you a TDS value that provides some hardness. I cut my rain-water with tap to give about 60ppm TDS for Apistogramma etc.

Because you are using CO2 I assume you are adding fertilisers? these will raise the TDS in the tank.

cheers Darrel

 

[Edvet]

pH changes due to "weak "acids don't harm fish as compared top pH changes due to strong acids (batteryacid and the likes).
Conductivitychanges should go slow, but then are not that dangerous i think. Compare what happens when whole forests flood and then dry up again.
My blackwater tank i sometimes drip in pure RO for 12 hours, no consequenses.
Just my 2 cts.

 

[sciencefiction]

My blackwater tank i sometimes drip in pure RO for 12 hours, no consequenses.

Yes, but you are dripping it for 12 hours. You are drip acclimating them for 12 hours!! Unless your fish are sick to start with and even then it's unlikely to get affected even if you drip acclimated them with liquid rock. A water change can take place in 5min in some scenarios like mine. Plus keeping blackwater fish that come from environment with 0 buffers and fluctuating ph is not like keeping fish that come from well buffered water with constant Ph. Some fish need those buffers in their water to stay alive and healthy. Yes, in nature Ph may fluctuate due to CO2 but that isn't changing the chemical composition of the water itself which is why Ph doesn't matter in most cases but it does when you don't know what's driving it to go all over the place.

 

[sonicninja]

This is really informative and interesting to read everyones opinions and advice. What would you suggest is a sensible TDS range to aim for on this tank? Im keeping Pygmy Corydoras, Celstial Pearl Danios and Otocinclus so any suggestions on what TDS I should aim for would be great, then I can simply mix my RO water/Tap water to achieve this value each time.

I am using ferts (I used to EI dose but have since changed to TNC all in one liquid fert. This would also account for a higher TDS reading in my tank.

It seems that I should do the following given the advice here:

-Ensure the TDS and temp of the water change water is consistent between batches and pay less attention to the pH alone.
-No-need to aerate if the water is standing for too long
-Ensure the water is dechlorinated (easily forgotten)

 

[sciencefiction]

I just wanted to ask, but what are the reasons you use RO water in the first place? None of those fish strike me as requiring too soft water or special water conditions to thrive. I've kept them/keep them in hard tap water with 50% weekly water changes besides pearl danios which I've never had.

 

[sonicninja]

Good question. Again partly due to forums suggestions and party due to my previous experiences of keeping these fish. As both the corys and the Otocinclus are south american species I always had more luck keeping them in softer water. The other reason is that being in central London the tap water has quite high nitrates and since im also adding ferts including this im only increasing it furthur.

I did ask this question on another forum recently as I was getting a bit boggled by all the info, someone suggested that my tap water conditions weren't suitable for the fish I was keeping. I'd also like to get the RO water situation nailed as in the future Id like to try my hand and Discus in an Amazonian biotope so its nice to learn from threads such as this before i get out of my depth.

 

[Edvet]

RO is only realy needed in rare occasions, breeding (eggs can be requiring low TDS) and some sensitive species. Most of the fish can tolerate higher values. Discus, especialy bred ones, can live in hard water no problemo. Keepintg the water clean is more important (do loads of wc)

 

[Sacha]

I have always used RO. I wouldn't even consider using London tap water to keep fish.

 

[sciencefiction]

Well, different people different experience and different conclusions.
My ottos have been doing great in hard tap water(Gh 12, Kh 8, Ph 7.4, TDS almost 300ppm) for the couple of years I've had them in one of my tanks with 50% weekly water changes. I had 3 pygmy cories for a year in another tank(because that's all they had in the shop) which were doing great until I changed the substrate one day with commercial soil and volcanic origin black sand which for one or another reason caused a disease outbreak in the entire tank within a couple of months including in the normal corys and platies. The pygmies and a couple of other corys didn't pull through by the time I realised it was the substrate but the rest are still alive as I binned the substrate.
So yes, pygmy cories are more sensitive but not to the water hardness. I know a person that massively bred them in water harder than mine.

Some strains of domestic discus are kept in hard water no problems. As someone says, it all depends on the fish you want to keep. People tend to say certain fish need soft water with 0 Kh to keep them and breed successfuly but for some mysterious reason they keep insisting all fish can live happily and breed in those conditions, that Kh and Ph don't matter, when on the contrary for some fish it matters and a plummeting Kh and Ph isn't well accepted by them.
The most obvious are for example mollies. Take some and put them in a black biotope tank that has acidic water and no buffers and we talk then if Ph and Kh don't matter.
Or try keeping your wild discus in hard water, neither will work.

 

[sonicninja]

Cheers everyone. Im going to check the TDS of my 70/30 mix sat in a barrel at home when i get back and see if its suitable. I've bought some JBL Aquadur in case i decide to go 100%.
Any suggestions on what TDS reading I should be mixing my water to obtain?

 

[Sacha]

Ah- see, if my tap water was GH 12, KH 8 and pH 7.4, I might consider it.

But it's GH 20, KH 16, and pH 8.2-8.4.

 

[sciencefiction]

Ah- see, if my tap water was GH 12, KH 8 and pH 7.4, I might consider it.

But it's GH 20, KH 16, and pH 8.2-8.4.

I'd imagine I would consider using RO with this water too. I mean, it's very hard cutting a proper size piece of it for a water change

 

[sonicninja]

Hi everyone,
So a little update. I've gone for a 70/30 RO/Tap mix resulting in a TDS of just under 100ppm. This is in stark difference to my tank TDS reading of just under 300ppm. I started making the transition of reducing the tank TDS last night by changing approx. 20% of the water using a section of 4mm CO2 tubing to basically trickle it in. So far so good and the TDS in the tank has dropped to 270ppm, I intend to continue to slowly introduce the RO/Tap mix over the weekend and into early next week to avoid any shock to the fish.

This leads me onto another question regarding the tank TDS and fertilisers. As I'm adding approx 1ml of TNC ferts to the tank daily 6 times a week this will as suggested increase the tank TDS. When I come to add my TDS 100ppm water to the tank each Sunday the water within the tank will have undoubtedly increased due to the ferts and i'll be back to square one where I'm adding a low TDS water to a high one.

Am I just getting a little confused? Although the ferts are registering on the TDS meter should I just presume that the 'base' readings of TDS in the tank will still be low? Not sure if ive explained that well enough.