Aquavitro Salinity alk concerns, anyone else using it?

[NWDiver]

Huh, weird that my alk reading is so much lower than yours.
I used two different elos kits and they agreed exactly, twice in a row.
I will post my bucket printout with the evening update.

 

[cptbjorn]

yeah my alk is still way up there at 10.8 and still reading consistently for the last 3 readings, which is odd because the water I have in my normal mixing bucket that has been mixing for a couple weeks now is still showing 7.0 and my test kit is matching the test solution. My bucket is an early batch, I got it the same week the first buckets started showing up in the stores around here so maybe they have made small changes or something...

The calcium is coming in line and is now probably within the margin of error for these test kits, but the Mg is still acting weird which sucks because its the only thing I can't really verify. Well I have a red sea Mg test kit but they are almost useless...

t=4:00
temp: 72.1F
alk: 10.8 Ca: 370 Mg: 1230

t=8:00
temp:70.5F
alk:10.8 Ca:390 Mg: 1155

t=16:00
temp: 70.3F
alk: 10.8 Ca:395 Mg:1170

 

[Boomer]

Be it know that Alk is difficult to test for and some Alk kits are FW and not SW. And there is allot of user error envoled.

I would assume that the rising Ca and Mg are caused by them being present as slightly soluble hydroxides which the test kits aren't picking up until they dissolve fully or react with dissolved CO2 or some other unknown factor.

Magnesium Hydroxide is almost insoluble, it is not like Kalk, calcium hydroxide. SeaChem uses Anhydrous salts which have dissolution issue at times and it just takes longer for them to dissolve and is why you are seeing the rise over time. Also, those numbers posted are within the "noise" factor of the test kit. Could some of that Mg++ be leaving a Mg(OH)2, yes. But remember OH- is part of the Alk.

 

[cptbjorn]

Interesting, thanks for explaining that. For some reason I didn't think about OH- being counted as alk but it makes sense now.

Also got two more data points and it looks like the alk is starting to do its thing, it is down a full point now.

t=32:00 temp:70.6F
alk:10.4 Ca:380 Mg:1170

t=64:00 temp:68.2F
alk:9.6 Ca:385 Mg:1155

 

[Boomer]

For some reason I didn't think about OH- being counted as alk but it makes sense now.

Often when you add a buffer there will often be a cloud. That cloud is usually a precip of Mg(OH)2, that really does not "harden" up and goes back into solution. Although OH- is part of the Alk it is only a very samll part.

 

[NWDiver]

Work had me running
So it seems there may be something to the low alk thing.
It looks like I will have to dose my mix water...
Today after a week I have:
Temp 76
pH 7.9
Alk 7
Ca 400
Mg 1300