Keep up KH and CA

[Myka]

Originally Posted by csaba911

Update-
Received replacement from ReSea it's about 20-30ppm different from Salifer.
Got from a friend a Seachem 425ppm reference solution, unfortunately it's 2 year old and both RedSea and Salifer read way to high value, near 520-550ppm
Is there any safe/sure way to home brewed calcium test solution?

It's the Red Sea Pro test kit? The expiry on the Salifert one is 2020? They essentially agree with each other, I'd believe them.

There is not a good DIY calcium standard you can make because calcium salts are hygroscopic, so you can't accurately tell how much water is in the CaCl when you weigh it. Maybe it would be "close enough" to get an idea (especially if you used a freshly opened tub of CaCl), but I wouldn't call it a "standard solution". The easiest and cheapest thing you can do is test your freshly mixed saltwater mixed at 1.0264 since each brand is usually predictable (unless you also just happened to have an off batch), and would provide you an answer that is at least as accurate as a homemade CaCl solution. Which salt do you use?