Myth or fact?

[Der_Iron_Chef]

Calcium dissolves (in the case of a calcium reactor) when the PH levels inside the reactor are brought down to a certain point through the use of CO2. This is how I understand it (please someone correct me if I'm wrong!).

The PH inside your aquarium needs to be much different than that inside a reactor, in order for your organisms to survive.

[midgetwaiter]

The only theory that makes any sense is that there is a lower pH in the sand bed when it is deep enough to create an anoxic zone and CO2 builds up. I've never seen any proof of this but if it were going to work this is what would have to happen.

[fencer]

Not CO2 but H2S is produced in DSB's. I have wondered if a Calcium reactor also releases Mg in sufficent concentration. Does anybody know here?

[Aquattro]

Originally Posted by fencer

Not CO2 but H2S is produced in DSB's. I have wondered if a Calcium reactor also releases Mg in sufficent concentration. Does anybody know here?

Mg will be released if it was originally a component of the media being dissolved. Whether this would be in an ionically availble species, not sure.

[Aquattro]

There will certainly be some dissolution of the substrate within our systems, but as I stated, not in any amount I would take into consideration. My understanding is that a pH of 7.7 is required to disolve Ca. My tank doesn't usually get that low. If things made of Ca started dissolving in my tank, I'd be worried about my Ca based inverts.
Now, in a 150g fully stocked SPS tank, I used about 20 pounds of reactor media in addition to kalk top off to maintain Ca and Alk per year. This tells me that anything comeing from the substrate is at best negligible.

[fencer]

Calcium reactors require pH 6.4 and 6.8 for proper release of Ca from substrate in the reactor. The reef water apparently has a higher buffering capacity so the low pH does not affect the tank pH

[Aquattro]

Yes, a reactor works best between 6.5 & 6.7. Ca will start to dissolve though in the high 7's. The low pH in a reactor is dripped back into the tank at such a slow rate that off gassing of the CO2 is quick and the high Alk will cover any other difference. Mainly though just dripping the effluent into the system flow will remove any CO2.