Testing kit giving weird numbers

[Tom-nanoreef]

I recently bought a salifert test kit because my old red sea test kit would give me inconsistent results, I did a spin test on my water box at my lfs, I got 8.2 alk. When I tested it myself after coming back my salifert I got 8-8.3 alk (tested 2 times). That was on the 18th, today I tested my alk and got around 6 twice. Is this a testing kit error or is it possible it dropped that much.

 

[Tom-nanoreef]

I recently bought a salifert test kit because my old red sea test kit would give me inconsistent results, I did a spin test on my water box at my lfs, I got 8.2 alk. When I tested it myself after coming back my salifert I got 8-8.3 alk (tested 2 times). That was on the 18th, today I tested my alk and got around 6 twice. Is this a testing kit error or is it possible it dropped that much.

I also only have soft corals

 

[Tom-nanoreef]

I also only have soft corals

According to the spin test, magnesium dropped after a week 200 ppt, is that possible with only soft coral and no real corraline growth?

 

[taricha]

When I tested it myself after coming back my salifert I got 8-8.3 alk (tested 2 times). That was on the 18th, today I tested my alk and got around 6 twice.

soft corals and many other calcifying organisms use Ca and alkalinity. not just stony corals. Not sure if the results are accurate, but it's not obviously wrong.

According to the spin test, magnesium dropped after a week 200 ppt, is that possible with only soft coral and no real corraline growth?

spin-test uncertainties are larger, because the sample volumes are so small. That is going to be just test kit uncertainty.