Go Back   Aquarium Advice - Aquarium Forum Community > Saltwater and Reef > Saltwater Reef Aquaria
Click Here to Login

Join Aquarium Advice Today
Thread Tools Search this Thread Display Modes
Please support our sponsors and let them know you heard about them on AquariumAdvice.com
Old 08-01-2009, 08:57 PM   #11
Aquarium Advice FINatic
Join Date: Sep 2008
Posts: 632
Originally Posted by Tank2379 View Post
Ok... So what your saying is I can't top off my Water with saltwater that's already prepared @ 1.026 since my water parameters are already @ 1.026?
This is where it's gone wrong. If some water has evaporated from your tank that started at 1.026, what remains in the tank is now higher than that. Maybe not enough to show up on the hydrometer yet, depending how much water we're talking about replacing, but over time it will go up without limit if you add salt every time.

gzeiger is offline   Reply With Quote
Old 08-01-2009, 09:00 PM   #12
Aquarium Advice Freak
RazorbacksFan's Avatar
Join Date: May 2009
Location: SouthWest AR
Posts: 533
Originally Posted by Tank2379 View Post
LOL... I understand the concept of water chemistry and quality just trying to start a debate.... but anyhow if I do weekly water changes and topping off during the week with RO water. How do I know if my Salinity will not raise with weekly water changes compared to topping off and my salinity staying at a steady 1.026? I mean I am using a Refactometer.
If you say take 50 gallons of water at 1.026 salinity out of a 100 gallon tank you add back 50 gallons at 1.026 that way in theory the salinity should be exactly the same. Does that help?

Go Team Insomnia!
RazorbacksFan is offline   Reply With Quote
Old 08-01-2009, 09:15 PM   #13
Aquarium Advice Activist
spikey's Avatar
Join Date: Sep 2008
Location: Melbourne Australia
Posts: 182
If you have a line for your water level and you top up with RO every day to that line; even if you don't test (I would not recommend) your SG should remain the same. If you top up to the line and then do your 'general maintenance' water change with sea water or pre mixed saltwater (I use sea water) your SG should be constant.

This very simplistic but you get my point.
spikey is offline   Reply With Quote
Old 08-02-2009, 02:19 PM   #14
Community Admin
melosu58's Avatar

Tank of the Month Award
Join Date: Oct 2004
Location: Virginia
Posts: 38,454
Also on a PWC you are taking salt out and then adding salt back in. On evaporation and top offs salt stays in and salt is added.


You can view many of my fish and corals in my photo albums in my profile.

View my tank

AA Community Rules|AA TOS

Forums 101 - posting, accounts, basics
melosu58 is offline   Reply With Quote
Old 08-02-2009, 03:13 PM   #15
Aquarium Advice Addict
SparKy697's Avatar
Join Date: Nov 2006
Location: Northwest Indiana
Posts: 1,495
Maybe think of it as a ratio. Since that is essentially what sg is. It’s a ratio of what a given volume of your water weighs compared to what the same volume of pure water weighs. Since we know that water and not salt evaporates, over time the ratio between water and salt will change. The ratio of salt to water in a given volume will now be a little higher. We correct that by adding pure water back to reset that ratio back to where we want it to be. If we used water that has salt added to the tank, we just added a little pure water plus some more salt. Depending on how long you wait between topping off, you may not see the change in the sg of the system the first time. Over time and repeated topping off with salt water you will see the sg of the system raise.

Water changes are just that. You are changing out some of the existing water with water of similar properties. Just like was mentioned earlier, this helps dilute some of the buildup of unwanted compounds as well as replacing trace elements that are needed.
"...but the guy at the LFS said I needed it!"
SparKy697 is offline   Reply With Quote
Old 08-03-2009, 10:33 AM   #16
Aquarium Advice Addict
Join Date: Aug 2006
Location: not here anymore
Posts: 5,338
Along the lines of what Razorbacksfan said...

Think of it this way. If you have a 10g tank at 1.026 and let 5g of it evaporate away, the water in the tank is NOT still 1.026 - it is quite a bit more. Now if you dump 5g of RO/DI water in the tank, you'll be back at 1.026. But if you dump 5g of saltwater at 1.026 into the tank, then you'll end up somewhere below where you were with 5g, but above 1.026.

If you're only replacing a little bit of evaporation each day, you won't see the rise in salinity even with a refractometer. But if you constantly replenish that evaporation with saltwater over the course of a week, you WILL see a rise in salinity.

Kurt_Nelson is offline   Reply With Quote

Please support our sponsors and let them know you heard about them on AquariumAdvice.com

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Other Benefits of Water Changes eatsomepopcorn Saltwater & Reef - Getting Started 3 02-01-2010 06:20 AM
Top-Off water? fshfrk58 Saltwater Reef Aquaria 5 10-27-2009 02:26 PM
RO/DI Top off water Phyl General Hardware/Equipment Discussion 13 07-29-2005 07:17 PM
Water change and water top off idea! sdveirs Freshwater & Brackish - General Discussion 8 05-17-2005 09:04 AM

» Photo Contest Winners

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -4. The time now is 12:06 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.