RO water and pH

Mr31415 · 08/05/2006, 05:20 AM

If I am doing the hyposalinity treatment - the RO water I am adding has obviously been aerated and heated to match the QT tank. Do I need to try and match the pH too using buffer in the RO water? Or is this not necessary?

pnosko · 08/05/2006, 09:17 PM

Do you mean for top-off to replace evaporation?

bertoni · 08/05/2006, 09:27 PM

There's no need to buffer RO-DI water. It doesn't have enough ionic content to change the pH much in any case.

carlsbl · 08/05/2006, 11:09 PM

Quote:

Originally posted by bertoni
There's no need to buffer RO-DI water. It doesn't have enough ionic content to change the pH much in any case.

Interesting....but if the PH is low out of the RO-DI filter, still low after the salt is added, how can I expect it to be on an acceptable level when added to my tank?

Brian

bertoni · 08/05/2006, 11:21 PM

The pH of RO-DI water is mostly meaningless, since it doesn't have any buffering or much in the way of ionic content. When RO-DI is added to the tank, the pH is set by the ion content of the water already in the tank.

If the pH is low after the salt is added, the water might need some aeration to purge excess CO2.

carlsbl · 08/05/2006, 11:26 PM

Quote:

Originally posted by bertoni
The pH of RO-DI water is mostly meaningless, since it doesn't have any buffering or much in the way of ionic content. When RO-DI is added to the tank, the pH is set by the ion content of the water already in the tank.

If the pH is low after the salt is added, the water might need some aeration to purge excess CO2.

Ah.....thanks. My other "hobby/career" is programming and networking, everything is pretty much absolute. Now this hobby, it's like the weather, who you ask, where you ask, how you ask........ugh!

Mr31415 · 08/06/2006, 01:53 AM

Yes I was referring to the RO water I mix to get to SG 1.009 - i.e. 1/5 of the tank volume in RO water. I found my pH was dropping to below 8.0 after I added my 3rd 1/5 RO water change. It used to be 8.35. I do aerate it before adding it to the tank.

Mr31415 · 08/06/2006, 03:55 AM

bertoni - I assume you were referring to the impact on pH when using RO as topup water? Because surely it will impact the pH of the tank when added in bulk for getting down to 1.009?

AZDesertRat · 08/06/2006, 11:33 AM

Mix it up with a powerhead and an air pump in it so you get good aeration. That should bring the pH back up.

bertoni · 08/06/2006, 12:42 PM

I don't think moving the SG to 1.009 should have that large of an effect on pH by itself, but I might be wrong. More aeration might be useful, and you could also ask in the chemistry forum.

08/05/2006, 05:20 AM	#1
Mr31415 Registered Member Join Date: Jun 2006 Location: Surrey, Canada Posts: 1,926	RO water and pH If I am doing the hyposalinity treatment - the RO water I am adding has obviously been aerated and heated to match the QT tank. Do I need to try and match the pH too using buffer in the RO water? Or is this not necessary?

08/05/2006, 09:17 PM	#2
pnosko Registered Member Join Date: Dec 2001 Location: Germantown, MD Posts: 3,584	Do you mean for top-off to replace evaporation? __________________ Looking for perfection in an imperfect world. Until one has loved an animal, a part of one's soul remains unawakened. ~ Anatole France (1844-1924) Current Tank Info: Dusty 110g, 55g & 29g tanks

08/05/2006, 09:27 PM	#3
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	There's no need to buffer RO-DI water. It doesn't have enough ionic content to change the pH much in any case. __________________ Jonathan Bertoni

08/05/2006, 11:21 PM	#5
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	The pH of RO-DI water is mostly meaningless, since it doesn't have any buffering or much in the way of ionic content. When RO-DI is added to the tank, the pH is set by the ion content of the water already in the tank. If the pH is low after the salt is added, the water might need some aeration to purge excess CO2. __________________ Jonathan Bertoni

08/06/2006, 12:42 PM	#10
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	I don't think moving the SG to 1.009 should have that large of an effect on pH by itself, but I might be wrong. More aeration might be useful, and you could also ask in the chemistry forum. __________________ Jonathan Bertoni

08/06/2006, 01:53 AM	#7
Mr31415 Registered Member Join Date: Jun 2006 Location: Surrey, Canada Posts: 1,926	Yes I was referring to the RO water I mix to get to SG 1.009 - i.e. 1/5 of the tank volume in RO water. I found my pH was dropping to below 8.0 after I added my 3rd 1/5 RO water change. It used to be 8.35. I do aerate it before adding it to the tank.

08/06/2006, 03:55 AM	#8
Mr31415 Registered Member Join Date: Jun 2006 Location: Surrey, Canada Posts: 1,926	bertoni - I assume you were referring to the impact on pH when using RO as topup water? Because surely it will impact the pH of the tank when added in bulk for getting down to 1.009?

08/06/2006, 11:33 AM	#9
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	Mix it up with a powerhead and an air pump in it so you get good aeration. That should bring the pH back up.