[reefburnaby]

Hi,

Excessive magnesium concentrations can cause the alk to drop and your pH to become unstable. The reason is because magnesium precipitates when magnesium ppm is too high and it brings the alk down along for the ride. Of course, your case isn't very servere since the magnesium isn't precipitating at a very fast rate (i.e. snow fall or calcium deposits on the glass). Without test kit for magnesium...it can lead to problems.

In the past (early 90s) magnesium ppm drop used to be a problem. This is because magnesium will slowly precipitate over time. However, new salt mixes have higher than normal magnesium levels to balance this effect. So, your friend may be correct in supplementing magnesium in the past, but it is no longer required today.

The reason why I am asking about the Xenia is because Xenia's actually don't do well with low pH tanks. It is just another indicator of low pH. In my experience, they grow like weeds in high pH tanks and very slowly in lower pH tanks.

I would take some of your tank water and put it in a bucket. Let it settle for a couple of hours and then measure the pH. This pH level is the pH of the tank water without CO2. If this level is higher than your usual measurements, then you probably have low water/air circulation.

I would also make a small batch of fresh salt water and measure that pH. If that pH is low...then well...you know what the problem is. Either the test kit is screwed or you have a bad mix.

Hope that helps.

- Victor.

[ 20 March 2002, 20:56: Message edited by: reefburnaby ]