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herring_fish
04/20/2015, 05:28 PM
I am in the process of rebuilding my system and I want my water chemistry to be as close to perfect and stable as possible, within reason. I want a very low maintenance, worry free tank.

To that end I am putting together a high end Calcium regulator/reactor setup and hope to get a lot of the trace elements that come from braking down coral skeleton. Using this collection of components purportedly fixes many of the issues that have been reported with calcium reactors like constant tuning and CO2 dumping. I have added a few details about the setup below but basically, I liked the concept because it better fits my personality so I have re-purposed my two part dosing system and jumped in with both feet.

My question is about magnesium and how to address this additive in concert with my new system. Some people add magnesium to the calcium carbonate media but I think that it would be hard to insure that you add enough or that you haven’t added too much. Other people have a second, smaller reactor in line with the recirculation water but using and keeping the right amount relative to that main media would be almost as hard. Still others people put a mag reactor on the effluent of the calcium reactor. Again, that would not be too controllable.

I had brief thoughts of having a second circulating pump on a mag reactor that was attached to the effluent but then I had a different thought…
As I think back to Randy Homes-Farley’s article on two part dosing, I believe he felt that adding larger amounts of magnesium, less often was OK, instead of dosing mag on a constant bases so dosing was done with two pumps, not three.

Am I way over thinking this? Should I just plan on dumping a measured amount of magnesium (slowly) in the sump every month? Has anyone else gone down this rabbit hole?



Some details of the setup for those who care.

Using a standard calcium reactor and CO2 cylinder, you add an AP digital regulator instead of a needle valve. Although AP says that this is never an issue I bought a two stage regulator instead of the one that is normally sold with it. This will prevent dumping when the cylinder begins to run low. Finally, a peristaltic pump that is rated for constant 24/7 duty, like a Masterfex or a heavy duty stepper motor driven hybrid, can push water from the main tank, through the reactor at a constant rate that will not decay with minor clogging at various places in the system as the media dissolves and migrates .

This makes for a constant pH in the reactor and a stable output of calcium, alk etc. New, this setup can cost more than 4 grand and buying parts of it that are used can still be a little pricy but it is rock steady, long term.

I will include the post that brought this to my attention but there are other ways to do it.

http://www.reefcentral.com/forums/showthread.php?t=2368618&page=42

bertoni
04/20/2015, 06:18 PM
The amount of magnesium consumed as a fraction of the calcium consumed varies from organisms to organism. This article has more details:

http://www.advancedaquarist.com/2003/10/chemistry

So the consumption ratio in tanks will tend to differ. Any calcium carbonate medium based on coral skeletons will have some magnesium in the mix. I think that some tanks consume enough magnesium that they need some dolomite in the calcium reactor, but that might be rare. I think you'll have to wait to see what your tank requires.

herring_fish
04/20/2015, 07:56 PM
Thank you for that article. It fills in a gaps in my understanding of how magnesium interacts in a different ways.

As I thought, depending on the studies that you relay on, the optimal range is pretty wide and forgiving and still accomplish its purpose.

I guess that's why you can get away with less consistency. Also, this article highlights how much individual tanks can vary, one from the next and from time to time in the same tank depending on what is in it.

I still wonder how best to address whatever requirements present them selves.

bertoni
04/20/2015, 08:29 PM
Water changes might be enough. They were for my systems. If not, I'd look into some dolomite, if I wanted to try some automation, although I wouldn't spend much money on the media, since it seems to be problematic in some cases, due to the difficulty of dissolving magnesium carbonate. It requires a higher pH than calcium carbonate.

herring_fish
04/21/2015, 07:48 AM
This may be a weird way to look at it but from what I could glean from the article and others that I have read, the effective differential between what calcium carbonate media can deliver and what various magnesium media additions can provide, can be around 10% but could vary widely to the high side or even having a negative relationship
.
If it the display tank’s needs were at the higher end and you had this calcium reactor set up, you could add a small used reactor for the mag media, with a much smaller pump and an inexpensive, standard intermittent duty peristaltic pump to feed it. From the bubble counter, you could also pull off controllable amount to go to the mag reactor so that it could be turned up or down as needed.

Of course this type of system is for maintaining concentration levels, not to bring them up but that could keep things nice a stable.