Questions about MG, and KH levels, and water changes

[Legonch]

Somewhat of a newb question here, but Ive been testing my CA, MG and KH every other day since I did a water change. The last water change I did was 20 percent 2 weeks ago today.

My calcium consumption has stabilized, and is not much with only zoas, one hammer, and one frog in the tank. Consumption is 10 per week on average. Current calcium is 420

KH changes about .4 over the same two weeks. Started at 8.8, today 8.4

My MG changed from 1500 to 1300 over the same two weeks.

First off, is this about normal for a 75 gallon tank without much coral? (tank is fishless at the moment)

Secondly, is MG lowering this amount a good signal that a water change is due?

Im slowly educating myself on my tanks consumption.

Thank you for the help.

 

[Andrew_bram]

I would retest mag. That seems like testing error.

 

[Legonch]

I just tested again, this time with a red sea kit, same result, 1290 MG

I am running carbon and gfo through a reactor, but that shouldnt pull out that much MG should it?

Any ideas?

 

[Fourthwind]

If this is a newer tank, I wouldn't bother running carbon and gfo unless you have a problem. It is possible (as I found out the hard way) to have a tank that is too clean. especially without fish in the tank.

 

[Legonch]

Tank has been up since october. Im running carbon and gfo mainly because of a phosphate issue. I have lace rocks, and they must leach phosphate constantly. Phosphate tests show 0 phos, but if I take the reactor offline, in a week hair algae starts showing up. Im only running the skimmer one hour twice a week since there isnt any fish. I do have a blood shrimp, and snails in the tank though.

Adjusted the MG to 1350 over the last 10 hours. I'll retest in a couple days to see where it is. Maybe my initial 1500 mg test was in error. Next water change Ill test with both red sea and salifert kits.

 

[Smiley]

which salt are you using? also know the effects of carbon/gfo.. they strip out a lot more than you think. lots to keep considering...

 

[Legonch]

I'm using instant ocean reef crystals.