Alk off

Reef_dachs · Sep 28, 2020

Hi,

I'm a bit new here. I've had a tank about 6 months. I'm having problems with my water chemistry. Specifically alk. I did a 15% water change in a 36 gallon tank yesterday. Used RODI & Instant Ocean Reef Salt.

Today my parameters are: (Salifert test kits)
PH 8.0
Phosphate 0-.03 (Can't tell)
Nitrite 0
Nitrate 5-10 (can't tell) - I must be color blind

Ammonia <.15
Alk 15.7
Calcium 385

Yesterday right after water change the PH was 8.3 & Calcium was 450

How can I get the alk under control and maintain the PH & calcium - what could be the quick drop?

laverda · Sep 28, 2020

It has been a while since I used instant Ocean salt, but I recall it being a bit hi in ALK and low in CA and Mag. It is a good idea to test your first batch of salt mix from a new bucket of salt. I used to mix Oceanic with IO to get a balanced mix years ago. Now there are salts the mix up much closer to what we typically want. RedSea is one that is reasonably priced.
You can reduce the Alkalinity of your new salt mix with acid. There are threads hear on that.

rmurken · Sep 28, 2020

lacynic said:
How can I get the alk under control and maintain the PH & calcium - what could be the quick drop?

This looks like a strong candidate for good old testing error. Alk of 15.7 is just not a normal number. And Ca dropping by 65ppm in one day is precipitous unless you have a huge Alk demand.

I suppose you could have a nutty batch of salt with off the charts alk that precipitated out with a bunch of your Ca but that seems far-fetched.

I’d test your alk and Ca again. I’d also mix up maybe a gallon of SW and test that too.

pH drifting is less of a concern. Focus on getting numbers you trust for the Ca and Alk.

Jojo92 · Sep 28, 2020

I hopped in this one hoping yours was low... no matter what I do so far mine is always low. I’m even doing a buffer with every water change. Like wtheck.

Reef_dachs · Sep 29, 2020

rmurken said:
This looks like a strong candidate for good old testing error. Alk of 15.7 is just not a normal number. And Ca dropping by 65ppm in one day is precipitous unless you have a huge Alk demand.

I suppose you could have a nutty batch of salt with off the charts alk that precipitated out with a bunch of your Ca but that seems far-fetched.

I’d test your alk and Ca again. I’d also mix up maybe a gallon of SW and test that too.

pH drifting is less of a concern. Focus on getting numbers you trust for the Ca and Alk.

The numbers were similar with the API kit too for calcium. I did not have one for alk. I normally get my water mixed from the LFS but was decided to make the water considering the tests were off.
For the alk test right before titration it will briefly turn pink and then right back to blue/purple.

Randy Holmes-Farley · Sep 29, 2020

Are you using tap water to make that new salt water? That can push alk too high.

Have you added anything to the aquarium in terms of supplements or pH control agents?

Randy Holmes-Farley · Sep 29, 2020

Jojo92 said:
I hopped in this one hoping yours was low... no matter what I do so far mine is always low. I’m even doing a buffer with every water change. Like wtheck.

It is normal to need to supplement alkalinity and calcium to a reef tank.

Reef_dachs · Sep 29, 2020

Randy Holmes-Farley said:
Are you using tap water to make that new salt water? That can push alk too high.

Have you added anything to the aquarium in terms of supplements or pH control agents?

I use RODI water. I added Seachem Reef Complete and Prime. If the PH drops I add Marine Buffer.