Sudden change of pH harmful?

[Stevetheadi]

Hi
The pH of my 64L tank was a high - pH8.

So I changed about half the tank's water with RO water, thinking that would start to bring it down.

But checked the pH and it's now pH6.5.

Is that too much of a change?

Should I change the water again and add some high pH tap water?

 

[seangee]

What type of fish do you have? High pH is often (but not always) an indication of hard water. If you have fish like guppies, mollies or platys they need hard water and if you use RO going forward you would need to add minerals. If you have softwater fish RO water (or a mix of RO and tap water is ideal. I only use RO in my tanks but keep fish that need very soft water - and my tap water is hard enough to walk on.

The value of the pH is not that important as long as it is stable over time. GH is the number that matters. To answer your question I would not change your water again immediately. If the change in pH causes shock to your fish it happens within minutes. An immedate change would just cause additional stress. If you want to use a 50:50 mix going forward its what you have now so use that in future. If you want to go back to tap water (or fully RO) just do a 10% daily change for a week using your target water. Week 2 you can do 20% every other day and then you can just make the switch.

 

[Stevetheadi]

I have harlequin rasbora, corydoras and cherry barbs.

I'll do as you suggest, not do another water change straightaway but make some gradual changes if I need to.

The water here is very hard so I'm limited as to what I can realistically do about the pH, I think.

 

[Stevetheadi]

I have harlequin rasbora, corydoras and cherry barbs.

I'll do as you suggest, not do another water change straightaway but make some gradual changes if I need to.

The water here is very hard so I'm limited as to what I can realistically do about the pH, I think.

 

[CassCats]

Slowly change pH.

Monitor your fish, don't change anything else again as the damage has been done if anything happened.

Always do small changes when messing with parameters. Slowly add the RO you need, not as much right away.

If your fish are going to have issues, they'll likely show problems within the same 24 hours from the pH change.

 

[Colin_T]

Acidosis and alkalosis both kill fish and are from a sudden change in pH.

Acidosis is where the pH drops rapidly.
Alkalosis is where the pH goes up rapidly.

Fish exposed to either acidosis or alkalosis will normally show symptoms within a few hours of being in the different water. However, symptoms are not always present.

Don't do anymore water changes for a week.

When you do water changes using water with a different chemistry, do small (10%) changes a couple of times a week. If you are trying to reduce the hardness of water by using reverse osmosis (r/o), mix the r/o with some tap water (50/50) and use that to do 20-50% water changes. Do smaller water changes if there is a lot of difference in the hardness.

 

[Stevetheadi]

Acidosis and alkalosis both kill fish and are from a sudden change in pH.

Acidosis is where the pH drops rapidly.
Alkalosis is where the pH goes up rapidly.

Fish exposed to either acidosis or alkalosis will normally show symptoms within a few hours of being in the different water. However, symptoms are not always present.

Don't do anymore water changes for a week.

When you do water changes using water with a different chemistry, do small (10%) changes a couple of times a week. If you are trying to reduce the hardness of water by using reverse osmosis (r/o), mix the r/o with some tap water (50/50) and use that to do 20-50% water changes. Do smaller water changes if there is a lot of difference in the hardness.

Thank you.

 

[seangee]

Going forward your water is indeed very hard, and your fish will all do better in soft water. I would suggest you aim for 50 - 75% RO mixed with your tap water. That way you don't need to worry about re-mineralisation, or any other additives. Personally I would go for 75% but 50% will make a definite difference to your fish health. Don't forget the tap water will still need to be de-chlorinated.

 

[GaryE]

The saving grace for you is weather. In the short term pools all those species potentially get trapped in (Corys in Amazonia more than cherry barbs or harlequins from more stable environments) water will get harder from evaporation. The rains come violently, causing floods (of up to 30 feet of rainwater in Amazonia)- super soft and quickly low pH. Your Asian species will experience monsoons, which are also rainwater floods. They are less likely to be trapped in bad conditions before though.

So a pH and hardness drop is in their genes. A sudden increase in hardness is more difficult to them. If they've survived 24 hours, they should be good.
Then slow and steady wins the race, and an RO/tap mix can bring the hardness down over a few weeks or months, to where you want it. I don't become concerned about pH (but I have the luxury of soft tap) and monitor tds or GH/KH.

 

[Stevetheadi]

Going forward your water is indeed very hard, and your fish will all do better in soft water. I would suggest you aim for 50 - 75% RO mixed with your tap water. That way you don't need to worry about re-mineralisation, or any other additives. Personally I would go for 75% but 50% will make a definite difference to your fish health. Don't forget the tap water will still need to be de-chlorinated.

Thanks, I'll do that.

 

[Stevetheadi]

The saving grace for you is weather. In the short term pools all those species potentially get trapped in (Corys in Amazonia more than cherry barbs or harlequins from more stable environments) water will get harder from evaporation. The rains come violently, causing floods (of up to 30 feet of rainwater in Amazonia)- super soft and quickly low pH. Your Asian species will experience monsoons, which are also rainwater floods. They are less likely to be trapped in bad conditions before though.

So a pH and hardness drop is in their genes. A sudden increase in hardness is more difficult to them. If they've survived 24 hours, they should be good.
Then slow and steady wins the race, and an RO/tap mix can bring the hardness down over a few weeks or months, to where you want it. I don't become concerned about pH (but I have the luxury of soft tap) and monitor tds or GH/KH.

The fish seem fine today so I guess no harm was done by the sudden drop in pH. I'll be more careful in future!