Make up water alkalinity dropping a fair amount

[l8_apex_it]

I noticed that my make up water in my garage has dropped in alkalinity significantly. I keep it running with a Rio2100 pulling in air and a heater. This current batch has probably been running for 4 weeks or longer. I noticed that after a recent water change on my tank the akl levels appeared to drop some. After testing my Seachem Reef Salts make up water this evening I found the levels to be around 2.0 meq/l if not less. Is this common? I guess I should use it sooner or just bump it up with sodium bicarbonate or the alk component from say ESV?

I'm curious as to the mechanism that causes the alk to drop. I know that calcium can precipitate out on heaters, pumps, etc. How would the alkalinity reduce?

Thanks!

[bertoni]

2.0 meq/L is very low. Did the water get hot? Higher temperatures encourage precipitation.

Calcium precipitates as calcium carbonate, which explains why the alkalinity drops so much.

[l8_apex_it]

Heat would explain it. The temperature was up to 90+ for more than a few days during the last heat wave. I will watch the parameters more closely next time.

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[tmz]

When calcium carbonate is formed each 20ppm of calcium preciptated is matched by approxmately 2.8dkh of carbonate alkainity.

[l8_apex_it]

I dumped the remaining water and there appeared to be a noticeable amount of precipitate on the bottom. So that goes along with what has been stated with heat.
Then today I read about Seachem and their high use of Borates. So that may be playing onto this as well.
Aerated new water for a day, added salt and have let that aerate for 1.5+ days. I will test tonight to see how fresh salt fairs.

[bertoni]

Okay, that sounds like a reasonable approach to me. The weather's been cooler here for a bit, so hopefully, you won't have a problem this time.

[l8_apex_it]

It might be time for a new test kit.?

The makeup water salinity measured at ~1.0245 (refractometer) and alkalinity measured 7 dKH. I was quite sure Seachem Reef Salt should be closer to 10 (or 9 as measured with additional borates).

So these results do make me question my Salifert tester. It is likely over a year old. I've been looking into the Hannah testers. Should I look into purchasing the hanna tester or just get another titration tester?

I need to resolve this as I've noticed the tank hovers at or under 7 dKH. I've been trying to bump it up and it will rise a little and then fall back down. Now I don't want to do anything too drastic until I know exactly what is gong on.

[bertoni]

The kit might be having a problem. I'd just get another titration kit, but the Hanna has gotten generally good reviews. Maybe a LFS will test your water in the meantime?

[l8_apex_it]

Looks like my test kit has expired. I took some water to a LFS (can I say names?) and they tested all my parameters (always nice to get a second set of eyes). Stated 7.5 dKH while the last reading I had was at 6.5. So while the results are off, they aren't off too much.

Surprisingly the Mg was at 1660 while I've been measuring 1440. May be time for a new Mg test kit too.

[bertoni]

Well, I'm sorry to hear that the test kits might need replacing, but those results are interesting.