Nitrate Destroyer -> Dissolved co2 -> Low Ph

Lil Puff · Aug 8, 2025

Hi guys, I have a predator reef tank thats struggling from low ph and large ph swings. Due to being a predator tank it has a crazy amount of nitrates being added to the tank so to combat that I have made a Donovan nitrate destroyer which has been working really well the past nine months give or take. I have 14 nitrate and 0.03 phosphate.

The only downside is the destroyer has reduced my ph a lot and is causing me to have large swings. From what I have read it is due to the anaerobic bacteria consuming the nitrates and releasing co2. I have added a refugium and ran my skimmer intake outside to help but its just not enough. My dads ph ranges from 8.2 at night to anywhere up to 8.5ph during the day and his tank is no less than 2 metres away from mine so I don’t think indoor co2 is affecting it at all.

Thanks everyone!

Below is a graph of my ph. The large drop in ph is from my skimmer being turned off.

Garf · Aug 8, 2025

Lil Puff said:
Hi guys, I have a predator reef tank thats struggling from low ph and large ph swings. Due to being a predator tank it has a crazy amount of nitrates being added to the tank so to combat that I have made a Donovan nitrate destroyer which has been working really well the past nine months give or take. I have 14 nitrate and 0.03 phosphate.

The only downside is the destroyer has reduced my ph a lot and is causing me to have large swings. From what I have read it is due to the anaerobic bacteria consuming the nitrates and releasing co2. I have added a refugium and ran my skimmer intake outside to help but its just not enough. My dads ph ranges from 8.2 at night to anywhere up to 8.5ph during the day and his tank is no less than 2 metres away from mine so I don’t think indoor co2 is affecting it at all.

Thanks everyone!

Below is a graph of my ph. The large drop in ph is from my skimmer being turned off.

No idea what your alkalinity is at but Increasing it will give a 0.04pH boost for every 1 DKH increase. Aeration is definitely your friend. Can you check the pH of the effluent of the nitrate reactor? Perhaps you could dribble that over some aragonite or feed it directly to the skimmer?