KH Levels too low-Not Sure Why

[SeaHorseQueen]

Hey,

So, I have low KH issues but I have no idea why. I'm about to do a water change to help the tank with nitrates and phosphates. My GSP Coral is nearly non-existent. Like it's down to just a tiny piece of tissue. Still light purple with pale flesh. Hammer Coral is fine and happy. I have no idea what's causing the KH to be so low and why it's shifting. I'm not sure whether it's time to start dosing or add baking soda. I'm taking a sample in to see what magnesium and calcium is so I will update that later.

My Tank Info: 20G H, will be 3yrs old in May, GSP has been with me for over a year. I just got the hammer a few months ago.

Here's my tests:

2/11 Salinity: 1.028 | Nitrate: 50.1ppm | KH: 2.5dKH | Phos: 0.82ppm

50% WC

2/18 Salinity: 1.025 | Nitrate: 57.5ppm | KH: 4.1dKH | Phos: >0.92ppm blinking

Water Top Off- Roughly a gallon

Tonight (2/19): Salinity: 1.025 | Nitrate: 52.9ppm | KH: 6.1 | Phos: 0.71ppm

My Hanna Checkers are nitrate and phosphate. The salinity is a refractometer. KH is Salifert.

Between last night and tonight, I only topped the water water off with RODI. I do need to bring the salinity down some more but I'm trying not to shock the tank or hurt the GSP Coral further. I have been trying to lower the phosphate by water changes but now the KH is low and the GSP is barely existing. I'll post a picture of what's left.

Hammer Coral

GSP Coral

What it used to look like

 

[Fish & Coral Store]

It looks like your fluctuating KH is causing stress on your GSP coral. Rapid shifts in KH (from 2.5 to 6.1 dKH) can destabilize the tank and stress corals, which is likely why your GSP is struggling. This could be caused by factors like low alkalinity in your salt mix, high nutrient levels, or coral consumption of alkalinity. To stabilize KH, start dosing alkalinity and aim for slow, consistent changes in your water parameters. Also, regular, smaller water changes with proper salt mix will help stabilize the tank without shocking the system. Keep an eye on nitrates and phosphates, as they also affect coral health.

 

[Randy Holmes-Farley Verified Community Expert]

What salt mix are you using? I’m suspicious about the alk measurement results.

 

[KStatefan]

What is your target for salinity?

You say it is 1.025 and you need to bring it down.

 

[SeaHorseQueen]

What salt mix are you using? I’m suspicious about the alk measurement results.

It’s the Fritz RPM Blue Reef Salt.

 

[SeaHorseQueen]

What is your target for salinity?

You say it is 1.025 and you need to bring it down.

I aim for 1.022-1.024

 

[Randy Holmes-Farley Verified Community Expert]

I aim for 1.022-1.024

Why so low?

 

[SeaHorseQueen]

Here’s the reading the store got tonight.

 

[SeaHorseQueen]

Why so low?

That's how I've always had it. I usually get 1.023

 

[KStatefan]

Between last night and tonight, I only topped the water water off with RODI.

Unless you a trying to raise salinity you should always top off with RODI

I aim for 1.022-1.024

I would target 1.025-1.027

I would also review your testing procedure for alk and make sure you are following instructions.

 

[Randy Holmes-Farley Verified Community Expert]

Everything will be lower if you target low salinity.

The posted sticky values seem OK, except magnesium, which would be partly low due to low salinity, but may well be a testing problem, which is very common. I'd ignore it for now. :)

 

[SeaHorseQueen]

Unless you a trying to raise salinity you should always top off with RODI




I would target 1.025-1.027

I would also review your testing procedure for alk and make sure you are following instructions.

I use the directions it's giving me and watched them do it. Same way I did it. I wonder if I need to wash out the plastic cylinder in between uses and not just rinse them. I only top off with rodi water. I only mix salt when I'm doing a water change.

 

[Randy Holmes-Farley Verified Community Expert]

What exact device are you using?

 

[SeaHorseQueen]

What exact device are you using?

For KH it’s the Salifert. Salinity is a refractometer. The other two are Hanna checkers

 

[Randy Holmes-Farley Verified Community Expert]

So this sentence was about a refractometer?

" I wonder if I need to wash out the plastic cylinder in between uses and not just rinse them."

 

[SeaHorseQueen]

So this sentence was about a refractometer?

" I wonder if I need to wash out the plastic cylinder in between uses and not just rinse them."

No that’s the KH test by Salifert. It comes with a small plastic unmarked cylinder to fill water up and start the test.

 

[BryanM]

I rinse all testing vessels with rodi water.

LFS test has your salinity higher, and at a better number IMO. I would calibrate your refractometer.

 

[Randy Holmes-Farley Verified Community Expert]

I agree, rinsing the collection cylinder with Ro/DI is fine.

 

[SeaHorseQueen]

I took some pictures this morning under the white light. To, it seems like it’s not as pale white. What do you think? I did a 10% WC and rinsed all of my glasses and test cylinders with RODI water. I had to wipe out the phosphate reader because it apparently couldn’t find the light to read it.

Last night before WC:

KH: 10.9 even after rinsing container with RODI water and dried it
Phosphates: 0.71
Nitrates: 54.2
Salinity: 1.024
Temperature: 78

I’ll update it later to see what it tests at. These fluctuations are crazy.

 

[BryanM]

LFS tests and your tests are wildly different... I'd probably ask the LFS to test again for you, and if their numbers are similar to their first test I'd be thinking you have some sort of testing issue.