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View Full Version : Water Change: How precise are your specs?


jasper24
08/20/2006, 10:55 AM
I have a 58G with about 13G in my sump. I do a 5G water change 1 x per week. Some times my "new" water is like 1 degree warmer / cooler than my display and the SG may be a little off. I keep me tank at 1.025 but sometimes my new water is 1.024 or 1.023 when I am ready to change. I have never seen any ill effects but was wondering if others are a little off or not.

leeweber85
08/20/2006, 11:10 AM
I don't think it really makes a difference, but I would try to get them as close as possible. If your specific gravity is off just add more salt/water till you get it right. I usually match Ph as well.

Ne0eN
08/20/2006, 11:25 AM
How are you measuring sg? Are you using a refractometer or a swing type device?

-- Rob

pad
08/20/2006, 12:50 PM
I use a swing arm to mix then switch to a refractomer for a final gut check. I also use a temp and PH meter to adjust close as i can without going too drastic. I have heard of some temp sensitive fish and corals, but i have not come accross them.

csb
08/20/2006, 01:09 PM
in a 10% water change, slight differences in parameters aren't going to change much of the overall picture. If the tank is at 78 degrees, and your new water is at 79 degrees, the net effect on the tank would only move the temp to 78.1. Not a big deal ... I usually heat my new water about 2 degrees above the tank anyway, because it cools a little bit during the water change process once I turn the heater off and usually I don't notice the main tank temp change much at all, beyond maybe .1 or .2.

Same for specific gravity ... even if you're off by a point or 2, the net effect on the tank is very minimal. Just get the params as close as possible!

Before a water change, I always check specific gravity, PH, temp, and ammonia! I've had to dump out 2 batches of water because of mystery ammonia.

davocean
08/20/2006, 01:14 PM
Why don't you just start measuring how much salt you use to hit 25?
Make you WC's easy, use the same containers and have a powerhead and heater set up for it.
Of course salinity will change with evaporation, but I do at least shoot for keeping it at 25.

jasper24
08/20/2006, 05:13 PM
I purchase my water change water pre mixed from my LFS. It is more expensive that way but I have been hesitant to get in to the world of RO/DI units. I get it as close as possible per my first post but it is never exact. I do use a refractometer but am not overly concerned if it is a little off. Like someone said in a 10% water change it will have very little effect. Just wanted to make sure that I was thinking correctly.