Calcium Dropping

[Gracee]

I tested my source water that I use to (re)fill the hot tub for ch. It tests ch=170. On more than one occasion, about 5 to 6 weeks after refilling the hot tub the ch tests so low that I can't test for it.

I didn't know that calcium could be lowered in the water without draining and refilling with water that had less. Where does my calcium go?

With new water in the tub I have virtually no foam but by the time the ch tests so low I have a moderate amount of foam.

Gracee

[quantumchromodynamics]

A phosphate pH buffer could cause the calcium to precipitate out. The most likely cause is testing error. Some metal ions will interfere with the test. What test kit do you have?

[carlee33]

Kent's recommended doses tend to be pretty enemic--especially the ones listed for Tech A&B (B-Ionic and Tech A&B are different by only about 3%, so the doses are interchangable).

I dose 28ml/day (1 fl oz) for my 37 gallon tank with a medium calcium load (2 medium sized SPS corals). If you go from pretty much zero calcium demand and add a couple frags, I'm not surprised that you noticed a difference!

While calcium test kits are always suspect, I believe in this case that there is an increase in calcium demand due to the addition of the new frags.

Try upping the dose to something like 15 ml/day and see how it goes.

[oldparr]

It happened to me too. At some point, I couldn't measure the hardness with a HTH test kit. Then I bought a Taylor K-2006 and I could measure it - the Calcium Hardness was 140ppm. I don't know what was wrong with the HTH kit. The sample didn't became red with the indicator.

My tub's calcium hardness was 180ppm right after the refill. I think my cover let some rain inside the tub. It's raining a lot here at Dallas area.