View Full Version : Always low mag and alk but not ca

09/25/2012, 04:14 PM
ok every time I test my mg and alk are low by a considerable amount but ca generally drops vary little. I dose using powder seachem and my coral all seam really happy but the dosage of Mg is getting ridiculous. Would a calcium reactor with higher levels of zeo mag and less calcium carb be a logical option for me? or would that just drive my ca off the chart?

09/25/2012, 08:13 PM
Something isn't right there. The calcium consumption should be a lot larger than the magnesium consumption. I would double-check the kits. Water changes with a low-magnesium salt could cause this problem. I had that problem for years, when using the old IO.

09/26/2012, 06:11 AM
The Alk should drop faster than Ca. Mg should not drop hardly at all. I only supplement Mg about every other month and then only a little bit as I like mine a little higher than what comes in my salt mix.

09/26/2012, 06:36 AM
What test kits are you using? Is there an expiration date? I would get a second opinion on those readings. I'd be very suspicious of your test kits. I would start by testing salinity using a good calibrated refractomer, both DT and make up. Once I know that's right, I'd retest my Ca, Mg and Alk with a good set of test kits, i.e. Salifert or the new Red Sea, both DT and make up. I wouldn't take any more actions, until I was sure of this information.

09/26/2012, 07:59 AM
i use salinity salt and have a good refractometer that I calibrate with 1.025 cal fluid. My mg test kit is an almost brand new red see test kit for alk i use a hana checker and calcium i use an api but have a red see kit on the way. I have had all my vallues verified by multiple test kits at my LFS and we both consistently get the same result range accross four or five different kits. Its been going on like this now for about six months.

09/26/2012, 05:18 PM
alk drops quicker, try dosing several times during the day

09/26/2012, 05:20 PM
I guess being my CA and Alk do drop my ultimate question is how much will a CA reactor do for MG

09/26/2012, 07:47 PM
If you're dosing a pH buffer, that could be a problem. They all add alkalinity, despite any advertising. It's impossible to raise the pH with an additive and not add alkalinity, by definition, because alkalinity includes OH<sup>-</sup> ions.

09/27/2012, 05:39 AM
no i dont dose anything based on PH if my PH is low I start by opening the window than testing alk mag and CA and figure out whats going on. I have made the PH buffer mistake before.

09/27/2012, 06:26 PM
Well, maybe if you started writing down the time and value for your test results, we could get some sort of trend line to understand what's happening. I'm still a bit confused.

09/28/2012, 05:54 PM
Ok so I have been looking at my numbers and it seams maybe its not really that my MG really depletes that much faster its just that the dose to replinish mag is a lot more material than CA or ALK like for example the recomended dosage for MG is 1 tsp per 20 gallons vs CA 1 tsp per 40 gallons and then even less at 1/2 tsp per 40 gallons so I think its just the ammount of mag I go through vs the others that keeps getting me thinking I am always burning so much mg. let me know if that makes any since.

09/28/2012, 09:24 PM
That makes sense. It takes a lot of magnesium supplement to change the level in a tank. This calculator might help:


The usual recommended limit is 100 ppm per day.

09/29/2012, 08:06 AM
yeah and i usually try not to do more than 50. Would a calcium reactor keep up with mag too?

09/29/2012, 02:26 PM
Probably. Getting the reactor to keep up with the magnesium content can take some tuning, though.

09/29/2012, 04:04 PM
well that be better than constantly dosing especialy since I am about to leave my gf in charge of it for seven weeks in jan.