What can influence a tank's Mg reading

[Delphinus]

Yeah, I got suckered again. I read post after post about how great a salt is and I think "I want to join this party! Please be my friend! I'm so lonely." It never works out. I kind of think a salt is just a salt. I dunno.

[JDigital]

I've been fighting to get my CA, Alk, and Mag up for that past 2 weeks.. Dosing every night any numbers just won't increase to the numbers I want... I don't have a packed SPS tank, so I don't know where all this could be going..

03/24/2009 Ca: 380-390 Alk: 6.4 Mag: 1155
03/25/2009 Ca: 370-380 Alk: 6.4 Mag: 1260
03/27/2009 Ca: 370-380 Alk : 6.4 Mag: 1110 NO3: Undectable
03/29/2009 Ca: 330-340 Alk: 7.4 Mag: 1230
04/01/2009 Ca: 380-390 Alk: 6.7 Mag: 1260

[Delphinus]

Could it be going out the skimmer? How's your skimmate production? The skimmer on this tank needs to be emptied everyday whereas my other 2 it's only once per week.

[Sebae again]

It could be going out the skimmer if you are not dosing to make up what you throw out. The big assumption with doing regular water changes is that water changes will make up for what is lost,so if you had a fish only tank it would work out as long as the fish never drank any water. The water changes only,with a good salt, make the new water on par with natural salt water. It you do only a ,10-20% water change it does nothing for the other 80-90% so every day our values become less and less. Unless we dose or do 100% water changes we will never win.

[Delphinus]

But I AM dosing right now, ie. not relying on water changes. I've gone through nearly a whole bottle of Mg so far this week and it's flatlined at 900. That's why I think it's odd? Why would the number not be going up at all. I'm using Tailored Aquatics Mg. 2 out of 3 tanks (with much heavier bioloads) are increasing, the one is not. Is there anything to watch out for that could be interfering with Mg or Mg testing?

[Sebae again]

Are calcium and alk up to par? Maybe take a cup of that tank water and see if you can get Mg up in that cup.

[StirCrazy]

ok, need some more info ont he tanks, what is in the ones that are good and what is in the one that is bad? (coral wise) also is there a sand bed in each tank and is it the same in each tank. are your Ca and alk the same in all 3 tanks? oh and is the low tank a new tank?

don't worry about the 24 hour mixing, as long as you are mixing it good it won't make a differance like that. and as long as it is mixed to the desolving poing it doesn't matter if it is 5 min or 5 days. once it is desolved it is desolved. I mix for 5 min with my drill propeller and then let the mag drive go for another hour. but after the 5 min with the propeller it is good.

I found DSB are good for sucking Mg out of the water. never had 1/2 the work to keep up Mg when I went bare bottom.

Steve