Low KH not affecting acropora, why?

[Bram852000]

Hey everyone, quick question about low KH levels:
A few weeks ago, I had a dosing pump failure that went unnoticed for almost a full week (I’m only home on weekends). When I finally tested, my KH had dropped to 4 dKH — definitely on the low side.

The strange thing is, despite keeping mostly SPS and Acropora, none of my corals showed any signs of stress or bleaching. It’s been almost three weeks since the incident, and everything still looks perfectly healthy. KH consumption has also returned to normal levels, which suggests growth hasn’t really been affected either.

So it got me wondering — is it the actual low KH value that harms corals, or is it more about the instability in pH that usually comes with it? I’ve been running a refugium on a reverse light cycle, so maybe that helped buffer the pH during the KH dip?

Either way, I’ve now installed an automatic KH tester to avoid this happening again. Just curious if anyone else has experienced something similar or has thoughts o
n this.

 

[Kooma]

I’ve had similar swings without noticing any effect on my SPS, my nem didn’t like it though. A slow decline like that is likely why it wasn’t an issue, if it were sudden I think the outcome would be different.

If your shopping fosters I run a versa, it’s the best money I’ve spent on my tank hands down next to programmable pumps and the radion.

 

[Boehmtown]

I run mine very low. I've found 2 things.... 1. As long as there's enough to buffer the pH, everything is fine. And the corals almost throttle down as the kh bleeds off, presenting the kh from continuing to plummet

 

[DanyL]

I had a similar situation where my dosing pump power cord got disconnected accidentally (it was still in the socket, just got slightly pulled away during maintenance, enough for it to not make contact).

In my case, in a high demand SPS dominated tank, after just a day my Alk plummeted from 8.5dKH to around 4.
While one Acropora did show some signs of stress - all the others were perfectly fine, and none died or even slowed their growth.

I think what really matters is how healthy and comfortable your corals are at the moment and accident like this happens.
If they are constantly struggling with an unstable environment than they are more likely to heavily stress when an extreme situation like this happens. However, a healthy coral is able to hold on and overcome an event like this fairly easily.