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HELP! pH drop after using R.O. water for the first time in 30% water change


Mamashack
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Am wondering if I have just made a huge mistake. Been having problems keeping the nitrates low in my shrimp and decided to try R.O.water as the nitrate in the tap water was 5 ppm and have been trying to keep nitrate at 10 or below as advised by the breeder.

 

Have just done my first water change using R.O.water as the base (TDS 4 - raised to 215 using salty shrimp - tank water TDS 280 before change and 260 after change, aiming for 250). Exchanged about 30% and now the pH has dropped from 7.8 to 6.8. Is this to be expected? Will it have harmed my shrimp? Should I have done a smaller exchange? Should I do another tap water exchange to reverse the pH dip?

Have also read somewhere that once you've started with R.O. water there's no going back to tap water - is this true? 

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Do you have aeration of the RO water you put in the tank?

 

It has lots of CO2 in it and would cause the pH drop temporary if use it directly.

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Can't believe I forgot to hit the "Follow" button!

@ James Aquatics - I did use it more or less straight away after remineralising it. I guess I should have waited.

Amazingly the shrimp were fine after the water change- if anything they seemed more active - definitely not dancing tho.

Now about an hour later, some are wandering about and grazing on stuff. Some look like they are hiding under the moss-balls tho a few have a tendency to do that when the light is on usually so not really a new phenomenon.

How can I avoid this happening in the future? Do I need to do smaller water changes? Adjust the TDS?

Is it normal for this to happen or I have missed something? Definitely used the water dechlorinator - is that still necessary with R.O.water?

@ bostoneric - I wasn't trying to lower the pH at all. I was trying to start with zero nitrate in the exchange water. The drop in pH was a huge surprise. Didn't think to check the pH of the replacement stuff - lesson learned! What proportion water change do you suggest in future?

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Can't believe I forgot to hit the "Follow" button!

@ James Aquatics - I did use it more or less straight away after remineralising it. I guess I should have waited.

Amazingly the shrimp were fine after the water change- if anything they seemed more active - definitely not dancing tho.

Now about an hour later, some are wandering about and grazing on stuff. Some look like they are hiding under the moss-balls tho a few have a tendency to do that when the light is on usually so not really a new phenomenon.

How can I avoid this happening in the future? Do I need to do smaller water changes? Adjust the TDS?

Is it normal for this to happen or I have missed something? Definitely used the water dechlorinator - is that still necessary with R.O.water?

@ bostoneric - I wasn't trying to lower the pH at all. I was trying to start with zero nitrate in the exchange water. The drop in pH was a huge surprise. Didn't think to check the pH of the replacement stuff - lesson learned! What proportion water change do you suggest in future?

 

No, dechlorinator is not needed for RO water, as it's pure water. the active carbon stage would remove it.

I do 25% water change weekly, after I gas out the CO2 for a day, I adjust the GH and perform the water change. pH swings less than 0.4

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well first get to the root of the problem, why are you having such high nitrates?

 

changing the water is just a bandaid.

The tap water is at 5 ppm and I'm trying to keep it under 10 ppm as I said in the first post. I wanted a zero nitrate start and had been suggested in another thread that R.O might be the way to go. Had no idea that the pH would drop so dramatically tho

 

I do 10%

Thanks countryboy I'll try that in future

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If I use RO water directly, my tank pH would go down.

If I wait a day, let CO2 out, and do the water change, my tank pH would go up a little.

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I agree with bostoneric. Make sure when doing a larger water change to match your parameters, from Temperature, PH, GH/KH, TDS, etc. Otherwise any large fluctuation that rapid could kill shrimp.

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No, dechlorinator is not needed for RO water, as it's pure water. the active carbon stage would remove it.

I do 25% water change weekly, after I gas out the CO2 for a day, I adjust the GH and perform the water change. pH swings less than 0.4

So aerating the water before using would gas off the CO2? Right I can do that. 

If I'm starting out with R.O water and using Salty Shrimp to remineralize can I stick with using TDS as the parameter? I'm more familiar with that altho I have just got a Gh test kit today.

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I agree with bostoneric. Make sure when doing a larger water change to match your parameters, from Temperature, PH, GH/KH, TDS, etc. Otherwise any large fluctuation that rapid could kill shrimp.

Thanks, DETA, that's why I panicked when I realised what had happened.

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So aerating the water before using would gas off the CO2? Right I can do that. 

If I'm starting out with R.O water and using Salty Shrimp to remineralize can I stick with using TDS as the parameter? I'm more familiar with that altho I have just got a Gh test kit today.

 

Yes, that's correct.

 

I will test the GH, and verify the TDS with that GH. later you only need to measure TDS.

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Have just tested the tank water and it is the same GH as it was before the water change - 11 dH

Just so I'm understanding what I'm supposed to be doing - I thought that doing water changes was to provide optimum water conditions so if I match everything what's the point in doing the water change? Was it wrong to reduce the exchange TDS so that it was nearer my target TDS of 250?

I hope that doesn't sound like I'm being defensive - I'm just trying to understand what I should be doing better

My target parameters for these neos are:

TDS 250 ppm

GH 7+

pH 7.5

nitrate under 20, ideally 10 or less.

temp 22-24C/72-75F

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I will adjust RO water to GH7, or lower and perform the water change.

 

so overtime, tank water GH will go lower, and reach your target.

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I'm not one who agrees with the TDS/GH pairing. I can easily get my rack system to have gh6 but it struggles to keep TDS over 100.

so to me testing for TDS when I remineralize is no good to me.  like what has been stated on another thread. when you mix your remineralized water you should let it sit for 24hrs so things are fully mixed with the water.

 

RO RO RO. I havent remineralized my rack system in close to 8 months.  and I dont do water changes either. all i do is top offs with 100% RO. my parameters are where i want them so i leave things alone.

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I will adjust RO water to GH7, or lower and perform the water change.

 

so overtime, tank water GH will go lower, and reach your target.

Thanks! I'll try that.

So, to recap suggestions so far;

smaller W/C of around 10%

let water stand a day or aerate to blow off CO2

get GH to around 7

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I'm not one who agrees with the TDS/GH pairing. I can easily get my rack system to have gh6 but it struggles to keep TDS over 100.

so to me testing for TDS when I remineralize is no good to me.  like what has been stated on another thread. when you mix your remineralized water you should let it sit for 24hrs so things are fully mixed with the water.

 

RO RO RO. I havent remineralized my rack system in close to 8 months.  and I dont do water changes either. all i do is top offs with 100% RO. my parameters are where i want them so i leave things alone.

And your nitrate levels been ok doing that?

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I'm not one who agrees with the TDS/GH pairing. I can easily get my rack system to have gh6 but it struggles to keep TDS over 100.

so to me testing for TDS when I remineralize is no good to me.  like what has been stated on another thread. when you mix your remineralized water you should let it sit for 24hrs so things are fully mixed with the water.

 

RO RO RO. I havent remineralized my rack system in close to 8 months.  and I dont do water changes either. all i do is top offs with 100% RO. my parameters are where i want them so i leave things alone.

 

If you use RO water, you can.

 

because you start from blank, nothing else in the water. for tank water, that's different story.

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Thanks! I'll try that.

So, to recap suggestions so far;

smaller W/C of around 10%

let water stand a day or aerate to blow off CO2

get GH to around 7

 

I disagree with 10% water change.

 

the reason is as following.

a shrimp tank produce waste (not just nitrate) everyday, for weekly water change, it accumulates 7x daily waste. 10% water change can only take out 1/10 of waste, overtime.

tank reaches a balance of 70x of daily waste concentration.

 

if you perform 25% weekly water change, so you take out 1/4 of total waste in the tank, overtime, the concentration level would stable at 4x7=28x daily.

 

rest of are correct.

 

PS, I knew some people never do water change, but there must a way to control the waste. if you don't have the method to control the waste, and never perform water change, you ask for trouble.

 

It also depends on colony size, feed routine, plant in the tank, plant trim, etc...

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James. what works for you doesnt mean its the only way.

 

I have a large sump with a huge refugium that handles all the waste in my system AND i've run across many others who are changing their water less and less now and have more success then they did doing 10% weekly.

I have 100s of shrimp and 0 nitrates and my other parameters are dead steady all the time.

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I think I'm going to have to sleep on this and look at all this again in the morning. It's beginning to get confusing, but that's probably because I'm tired

I guess I'm going to have to find out what works for my shrimp and stick with it as long as there aren't any problems.

Thanks for your insights everyone who answered!

Night night.

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