[TestSubject]

Hello everyone, I'm new to this forum as chemistry is not my everyday field. I hope I`m posting this in the right section and than all of this makes sense. So here goes :

I`ve got, a soon to be, saltwater tank in which I've placed DIY Portland Cement rocks. These have been soaking in water with regular water change for a while but they are still affecting the water Ph. The targeted Ph for the tank is 8.3 but the rocks bring it to 9.5 and up.

From what I understand of my research it`s the Calcium Hydroxide in the cured cements which is sightly water soluble that affects the Ph and takes a long time to leach out.

I would like to know if their is a way to neutralize the Calcium Hydroxide into Calcium Carbonate which is a beneficial salt for the water. All this in the goal of have a stable Ph.

I`ve read that Carbon dioxide can be use for the reaction but its a two way street as to much of it and it will dissolve the salt.

I would greatly appreciate any help understanding this process and tips or idea on this issue.

Thanks

Alexandre

[Hunter2]

If you can only use Carbondioxide you need an automatic system. You need a pH-controller which controlls a valve to release carbondioxide to the solution. Additionally you need a good circulation pump.

[TestSubject]

Thanks for your quick reply.

I'm not limited to Carbondioxide, I would like that the byproduct of the neutralisation and the acid are both safe for the marin life so that if there is any left after the water change I don't have to stress.

I brought up Carbondioxide because it's the first candidate I found. I kept doing some research, maybe Carbonic acid or Iodic acid (I believe the byproduct would be 2x I^- which is beneficial as well) would be simpler?

Alex

[Borek]

I brought up Carbondioxide because it's the first candidate I found. I kept doing some research, maybe Carbonic acid would be simpler?

In this context carbon dioxide and carbonic acid are the same thing.

[TestSubject]

Yes this is what I found out with further reading. I also looked at Iodic acid as well, since I believe the byproduct is I^- (iodide), if I'm not making a mistake.  Iodide is also beneficial.

Alex

[Borek]

Traces of iodide are OK, but you will need way too much to change pH. Plus, hydroiodic acid is expensive.