RO\DI Water - Top Off and Water Changes

dannable · 10/16/2006, 08:23 AM

So for my 35 Gallon FOWLR..

I am thinking of using RODI water.

1) How often should I do a water change and how much?? I have heard 10% every week.
2)Can I just dump the RODI water in without any treatment with PRIME or any water conditioner?
3)Is the PH of the RODI not going to be significantly lower than the PH of the water in my tank?

The tap water in my area is known for its high quality (according to the local brewers

. If it tests low for phosphates would it be ok to use it for water changes and top offs?? I am using carbon so metals should not be an issue.

Your help is appreciated.

doox00 · 10/16/2006, 08:45 AM

I would always use ro/di in a saltwater tank. Some use tap without issue, but more times than not you hear about poor water quality, loss of life, algae problems etc with the use of tap.

15-20 percent every 2 weeks is good, or 10 percent a week is also good for water changes.

You can add the ro/di water into the tank, no treatment is required.

Shagsbeard · 10/16/2006, 08:55 AM

Top off with fresh water... do water changes with salt. You are probably aware of that, but I just thought I'd be sure. Keep a reading of your SG current before and after any water change, or during a long period without any water changes.

dannable · 10/16/2006, 08:55 AM

What about the PH?? Is it not softened water as well?? Do I need to make any adjustments for this?

MCary · 10/16/2006, 10:05 AM

RO water has no buffering capacity. Buffering is the ability of a solution to resist a pH change. That is basically what you are measuring with kh test. In that test you add a pH indicator that changes color once the solution reaches a particular pH. Then you drop in acid and see how much acid the solution will take before the pH changes and colors the indicator. With RO water a single drop of acid changes the color. With salt or hard water it can take many. What this means is that a single drop of a base (saltwater) also cause a big swing toward the high pH. So simply put, the RO does not lower the pH of the saltwater, the saltwater raises the pH of the RO. And there is plenty of buffers left over in the water so there is no dillution effect.

Mike

dannable · 10/16/2006, 10:49 AM

Thanks Mcary. Now I have to tell my wife about the new addition to our budget

BORNTOFLY · 10/16/2006, 11:23 AM

RO/DI will make a huge difference in that you can control water quality. Make sure to get a decent unit as it makes a big difference. You can get some great units from the RC sponsers here in the 150 to 200 range. For such a small tank you could go with a 75 GPD and be very happy Also make sure to get a TDS meter so you can test if RO/DI unit is working correctly.

Rick

10/16/2006, 08:23 AM	#1
dannable Registered Member Join Date: Aug 2006 Location: Guelph Ontario, Canada Posts: 430	RO\DI Water - Top Off and Water Changes So for my 35 Gallon FOWLR.. I am thinking of using RODI water. 1) How often should I do a water change and how much?? I have heard 10% every week. 2)Can I just dump the RODI water in without any treatment with PRIME or any water conditioner? 3)Is the PH of the RODI not going to be significantly lower than the PH of the water in my tank? The tap water in my area is known for its high quality (according to the local brewers . If it tests low for phosphates would it be ok to use it for water changes and top offs?? I am using carbon so metals should not be an issue. Your help is appreciated.

10/16/2006, 08:45 AM	#2
doox00 Premium Member Join Date: Feb 2006 Location: West Michigan Posts: 928	I would always use ro/di in a saltwater tank. Some use tap without issue, but more times than not you hear about poor water quality, loss of life, algae problems etc with the use of tap. 15-20 percent every 2 weeks is good, or 10 percent a week is also good for water changes. You can add the ro/di water into the tank, no treatment is required.

10/16/2006, 08:55 AM	#3
Shagsbeard Registered Member Join Date: Jul 2006 Location: Morro Bay, CA Posts: 2,143	Top off with fresh water... do water changes with salt. You are probably aware of that, but I just thought I'd be sure. Keep a reading of your SG current before and after any water change, or during a long period without any water changes.

10/16/2006, 10:05 AM	#5
MCary Premium Member Join Date: Dec 2002 Location: Hardin, Montana Posts: 3,142	RO water has no buffering capacity. Buffering is the ability of a solution to resist a pH change. That is basically what you are measuring with kh test. In that test you add a pH indicator that changes color once the solution reaches a particular pH. Then you drop in acid and see how much acid the solution will take before the pH changes and colors the indicator. With RO water a single drop of acid changes the color. With salt or hard water it can take many. What this means is that a single drop of a base (saltwater) also cause a big swing toward the high pH. So simply put, the RO does not lower the pH of the saltwater, the saltwater raises the pH of the RO. And there is plenty of buffers left over in the water so there is no dillution effect. Mike

10/16/2006, 10:49 AM	#6
dannable Registered Member Join Date: Aug 2006 Location: Guelph Ontario, Canada Posts: 430	Thanks Mcary. Now I have to tell my wife about the new addition to our budget

10/16/2006, 11:23 AM	#7
BORNTOFLY Premium Member Join Date: Nov 2005 Location: Columbia, SC Posts: 112	RO/DI will make a huge difference in that you can control water quality. Make sure to get a decent unit as it makes a big difference. You can get some great units from the RC sponsers here in the 150 to 200 range. For such a small tank you could go with a 75 GPD and be very happy Also make sure to get a TDS meter so you can test if RO/DI unit is working correctly. Rick