Water Parameters

[returnofsid]

Okay, I've recently got a used RO/DI unit....barely used. I've got some questions about water parameters now though. I just tested my SW tanks, my tap water and then my RO/DI water (before and after adding salt to 1.025). I was under the impression the an RO/DI unit didn't effect Ph but the Ph between my tap water and fresh RO/DI water is sure a lot different. In fact, a lot of parameters change depending on which water I'm testing. I'll list test results for all water for the following...Nitrate, Nitrite, GH (for fresh water), Alk and Ph. Please let me know if you see any problems. Both of my SW tanks tested the same. One of my tanks contains Crushed Coral and the other contains Aragonite Sugar Sand. They both have LOTS of live rock, soft corals and LPS. Listed below are my test results.

Tap Water

Nitrate = 20
Nitrite = 0
GH = 150
Total Alk. = 180
Ph = 8.4

Fresh Ro/Di Water

Nitrate = 0
Nitrite = 0
GH = 0
Total Alk. = 0
Ph = 6.2

Ro/Di with Salt added to 1.025

Nitrate 0
Nitrite 0
Gh (not tested)
Total Alk. 0
Ph 8.4

Aquarium

Nitrate 0
Nitrite 0
Total Alk. 180
Ph 8.4

Why am I getting such a difference in Gh? It would seem that the Ro/Di unit is changing my Ph, Alk and GH. I understand that adding the salt to the Ro/Di water is bringing the Ph back up to 8.4. It would also seem that there is something in my aquarium that is definately changing my Total Alk....putting it back at the level of my Tap Water. Oh, one more piece of information that may help. I've used Tap Water for my aquarium until I recently purchased the Ro/Di unit. Since then, I've been doing 5 gallon water changes using Ro/Di water. I've done 5 gallon changes every night for the past 4 or 5 nights. I'm going to start doing 15 gallon changes each night though. Unfortunately, I don't have a water storage container so am limited to buckets...lol. I'll soon be purchasing a large garbage can to use as a water storage tank.

 

[returnofsid]

Well, after posting, I gave Kevin a quick call. I ran down all the parameters to him and I guess I need to use a different test kit, especially for Alk. I'm using a brand new Jungle 5 in 1 dip strip kit and from what I understand, they're not all that good.

 

[CarlaW]

Salifert :d :d :d :d

 

[Boomer]

return

You can not measure the pH of RO/DI water. There is nothing in the water for the kit/meter to respond to, so you get a fasle reading, which may be almost anywhere.


GH = General hardness. It is the sum of all the calcium, magnesium, strontium and barium in water. Your RO/DI has removed it. It is suppose to and should read zero. GH test kits do not go high enough to measure it in seawater usually. The kit would need to go to up like 7000 ppm or so.

Your RO/DI water should also show zero ppm for Alk. When you mix the salt in with the RO/DI water the Alk should take on the Alk of the salt mix. Your new seawater, before you put in the tank, should not read zero. There is something is wrong with either a testing error or the kit is bad. Take note that your Alk for tap water and the tank are the same. That is not right at all or lets say it is rare to get the same number

 

[returnofsid]

Well, I did 3 seperate tests on each water sample and came up with the same exact results every time. I understand that my tap water and the water in my tank shouldn't show the same Alk, but either they are the same, or all of my brand new test strips are off by the exact same amount...lol. I'll have to wait until I can afford some good Salifert test kits to do more accurate testing. Hopefully soon. In my first post, I should have mentioned the brand of salt I'm using as I know that does matter. I'm using Instant Ocean. I understand that it's a little low on some elements.

 

[NaH2O]

I wouldn't rely on the test strip results. See if you can find someone to verify your test results with a good test kit (i.e. Salifert).

 

[Boomer]

Yah, test strips, not a good idea. The Alk of IO is around 180 ppm and there is no chemical reason for it to read zero in the new mix. And with a pH of 8.4 it can not be zero.

 

[returnofsid]

I'm hoping to take some water samples to Kevin to get tested today.