Ph in deep sand bed

Zero Nitrates · Jan 1, 2017

What is the ph in a deep sand bed compared to the ph in the water in an aquarium?

saltyfilmfolks · Jan 1, 2017

imo, its going to vary depending on where in the bed you are. areas of good flow will be different than no low flow. but overall Id assume it to be close to tank water.

nervousmonkey · Jan 1, 2017

@Lasse measures this actively on his system as well as ORP I believe.

Lasse · Jan 1, 2017

For the moment - I´m not measuring the pH in my DSB but I measure the ORP below the DSB (I have a type of undergravel filter plates at the bottom and a very slow counter flow through the bed.) It’s a steady flow of around 4.5 litre a day (1.2 gallon/day) and I could be more if the ORP will go down.

I´m planning to measure pH below the sand bed in the future – has some problems to do it in the middle of the bed with the type of construction I have now. I´m going to switch to ProfiLux 4 and when I do that - i will also measure the pH under the DSB.

Generally spoken – If there is a bacterial activity in the bed – the pH should be lower in the bed (compared with the aerated water) (excess of CO2). However some processes give a higher pH – as an example – denitrification.

With other Words - it depends on there you measure your pH in the bed.

My thought is that the pH can be far lower than 7.6 an therefor can a DSB serve as a rather slow calcium reactor if there is a counter flow through it (counter flow – from bottom to the Surface)

Sincerely Lasse

Zero Nitrates · Jan 1, 2017

Thanks @Lasse
Very interesting information you are compiling.
I was curious about the top three inches of a dsb having lower ph because of the excess CO2 from all the bacteria and critters.
I wonder how well it would work as a natural calcium reactor. (Have some aragonite mixed in)

skim · Jan 1, 2017

A while back I contacted CaribSea and asked about the Reactor media which is the same as the substrate just crushed a little more. I wanted to know at what PH that the Media starts to dissolve and I was told it will start to dissolve at 8.2 at very small amounts and as ph drops the faster it dissolves.

Lasse · Jan 1, 2017

skim said:
A while back I contacted CaribSea and asked about the Reactor media which is the same as the substrate just crushed a little more. I wanted to know at what PH that the Media starts to dissolve and I was told it will start to dissolve at 8.2 at very small amounts and as ph drops the faster it dissolves.

Normally, it is estimated that calcium carbonate begins to dissolve around a pH of around 7.6 - 7.8. It differs little with regard to other substances found in the limestone.

In a calcium reactor - you normally have a pH around 6.6.

I wonder how well it would work as a natural calcium reactor. (Have some aragonite mixed in)

I know from other people who had the DSB for a few years that it consumes a lot of substrate per year. I think it takes quite a long time because it needs to be built up much of organic matter bacteria can work with (and produce CO2).

In my case, I have prepared so that I can add CO2 under the DSB if I need

Sincerely Lasse

Zero Nitrates · Jan 1, 2017

Thanks @Lasse
I am reading your build thread right now. Thank you so much for sharing your experience and knowledge.
Sincerely
Kyle

Randy Holmes-Farley · Jan 2, 2017

Zero Nitrates said:
What is the ph in a deep sand bed compared to the ph in the water in an aquarium?

Lower, typically, but how much lower will depend on many factors, including the type of sand. Mine was in the mid 7's

Randy Holmes-Farley · Jan 2, 2017

skim said:
A while back I contacted CaribSea and asked about the Reactor media which is the same as the substrate just crushed a little more. I wanted to know at what PH that the Media starts to dissolve and I was told it will start to dissolve at 8.2 at very small amounts and as ph drops the faster it dissolves.

They are wrong. Seawater at pH 8.2, 6.5 dKH and calcium of 420 ppm is substantially supersaturated with calcium carbonate and substrate will not dissolve unless the local parameters are lower. It needs to drop into 7's for any dissolution.

Randy Holmes-Farley · Jan 2, 2017

Zero Nitrates said:
Thanks @Lasse
Very interesting information you are compiling.
I was curious about the top three inches of a dsb having lower ph because of the excess CO2 from all the bacteria and critters.
I wonder how well it would work as a natural calcium reactor. (Have some aragonite mixed in)

It works some long term, but cannot keep a reef tank with substantial demand from dropping in alk.