Tetra KH vs. Salifert KH - tank in shambles

[belgian_waffleman]

I have been having some issues with my tank. Corals didn't look their best, so I did a water change and a day later I did a full battery of tests and my MG and calcium seemed way low and KH was 8dKH. Measure with my Tetra Kit. (Ph= 8.15)

so I figured that I will have them re-checked at the local LFS in the morning. They measured my KH and it read over 15dKH

I switched to a different salt instead using the "cheap" IO salt and have done 3 big water changes with the new salt (50% each) over the course of 4 days. My corals have stopped dying but they sure don't look happy. it looked like RTN , but even on some LPS's.

I have greatly reduced my daily Alk supplement to 60ml's instead of 180 ml's. I kept the Calcium addition at 200ml's per day.

I finally got my own Salifert test kit, and I measure 12dKH instead, while my Tetra KH test kit reads 8. The calcium is still at 240 ppm and Mg is 1100ppm. Salinity is 1.024, Ph=8.12.
I find it strange that these numbers are still off like that especially after the 3 massive water changes with Oceanic Salt, which is supposed to be high in Mg. and Ca.

Are all my readings off because I have extremely high KH? Is the Soda Ash messing with all the readings?

I guess I should stop dosing ALK (BRS soda ash in 1 gallon solution) until KH is 8 or 9?
I will throw my tetra test kit out. It is several years old so who know when it went bad. My number has been 7 or 8 pretty consistent for years

Any suggestions or comments?

Waffleman

 

[sedorusc]

Did you test the fresh made water to get a baseline level of the salt mix contents?

 

[Dave VG]

SG is a little low. Should be 1.026 and that will affect LPS and some SPS. I know this to be true form a first hand experance with low SG due to a swing arm many moons ago. I'm no chemest so i'm not shure if high ALK could throw off the other tests. My guess would be no but that is just a guess. sedorusc has a good point.

 

[belgian_waffleman]

I forgot that the Ca was only measure at half scale. so the number for calcium is 480ppm. The Mg tests 1200 now, since I added more magnesium mix last night.
The other numbers are what they are.

The salt mix has KH= 11dKH, Ca = 460ppm, Sg=1.025. I didn't check Mg. on that one yet, later I will re-test.

Waffleman

 

[Gary Majchrzak]

I guess I should stop dosing ALK (BRS soda ash in 1 gallon solution) until KH is 8 or 9

definitey stop dosing alkalinity supplement until dKH drops. Keep in mind that both IO and Oceanic both mix up to 10 or 11dKH- so frequent large water changes may actually prevent your alkalinity from droppoing as quickly as it would on it's own.

FWIW: Oceanic and Reef Crystals can be pricey. I continue to have great success with "cheap" IO spiked to optimal params with Prestone Driveway heat (calcium chloride) and magnesium chloride ice melter.

In summary, the problem here was a bad test kit- not bad salt mix.

 

[belgian_waffleman]

Thanks Gary for the input . I'm also blaming the test kit at this point. I'm going to stick with Oceanic for while and see how it is. It supposed to be more consistent.

I'm starting to see some polyp extension on my teal acro. We wait and see for now. no more drastic changes.

I'm planning a total tank reset, more to follow on that...

Waffleman