Old test kits vs. new test kits

[mfinn]

I just purchased new Salifert ALK, and CA test kits because the old ones were getting low on reageants and the experations dates were coming up.

On Wedesday this week I tested with the old kits

ALK = 9.1
CA = 425

Today I rested with the new kits

ALK = 10.3
CA = 500

I tested twice with the same numbers coming up.

I then tested with the old kits and I got almost exactly the same as I did 2 days ago.
The old CA test kit has a experation date of 09-2010
and the old ALK test kit has a experation date of 05-2010


Why some much difference when the old test kits weren't past the experation date?

[fishchef]

I have found that Salifert Tests read low when their about a year old...go figure. Its always a good idea to double check with an LFS or another brand of kit. I've been using Salifert for a long time, but I also like API to compare. Their cheap, too.

[bertoni]

Testing is a sore point for a lot of people. I don't have any very strong recommendations for accurate kits for alkalinity and calcium at this point, due to all the problems people report. It's possible to make a DIY alkalinity kit that's reliable, although it requires a good pH meter. I can post a link to instructions, if you're interested.

[mfinn]

Testing is a sore point for a lot of people. I don't have any very strong recommendations for accurate kits for alkalinity and calcium at this point, due to all the problems people report. It's possible to make a DIY alkalinity kit that's reliable, although it requires a good pH meter. I can post a link to instructions, if you're interested.



Thanks.
I don't have a ph meter.
I normally don't test much.
I've always relyed on just regular water changes and never really bothered with ca, alk, and mag testing or adding in my soft coral tank or my zoanthid tank.
I decided to try keeping those levels up in my zoanthid tank, and see if there is a difference over the long run.
I have a few friends that swear by it ( higher levels than just Reef Crystal gives) with their zoanthids.
I know there has been issues with many hobby test kit brands, but when both of my older test kits had lower test results than the new ones, I was curious if I should believe the new test kits.

[mrrogers]

I personally like the API kits. They seem to be pretty accurate when referenced against my LFS

[HighlandReefer]

I agree with Jon.

The most accurate mesurement for alk testing IMHO, is to use the acid titration used by Randy.