unstable alkalinity

[radium]

My 135G reef is about a year old, and Im having a strange problem. My alk has been stable at 3.7-4.0 meq/L with 400ppm cal, consistently. Recently I've been having trouble with it falling below 3 meq/L.

I checked the alk the other day and it was at 3.0 meq/L. I dosed seachem reef builder for the next day and got it back to 3.7meq/L. Twenty four hours later, the alk is back to 3.0 meq/L.

The alkalinity is falling off fast, but the calcium remains stable at 400ppm. I'm using a dual geo calc reactor with plenty of media. I tested the alk of the effluent, just for kicks, and it is off the chart. The effluent pH is 6.5.

I understand calcium and alkalinity exist at a balance. Typically when I "rebalance" the alk and cal, the reactors balanced additions keep things stable. I find it odd that my calcium is stable, yet the alkalinity is not. Could this be a magnesium problem? I do monthly 30 gallon water changes.

Does anyone have any ideas as to why my alkalinity is suddenly so unstable?

 

[jmeader]

Yes. It could be your magnesium. That's the problem I start having when my mag gets down to 1000ppm.

 

[justme94]

FWIW, Butch (jmeader) was helping me with a problem I had with my levels and told me about magnesium. Upon testing, my mag was at 900. I slowly bumped it up to 1320 and I've never had my calcium and alk levels be this stable. I can only attribute this to the fact I got my mag level up to par.

HTH

Stephanie

 

[radium]

I checked my magnesium today, with a salifert kit. I'ts right at 1200. I'm not sure how low it was before my recent water change. I'm going to dose up to 1300-1400 to play it safe, but I haven't found any info claiming a mag level of 1200 would cause alk problems like I'm having.

 

[jmeader]

A mag reading of 1200 is alright and would not cause your problem. I think your effluent may be causing it.

 

[radium]

Thanks for the mag info.

What do you mean by the effluent's causing it? Too low of an output? Is there any way I can test the effluent? The readings are off the scale for both calc and alk, which I guess is what youd expect.

I remember reading that your effluent alk should be 1 meq/L higher than the alk youre aiming for in the tank, but I don't know if that's a good guideline or not.

 

[jmeader]

I'm not familiar with calcium reactors, so I can't help you troubleshoot or fine tune it. I don't see how your alk could be off the scale with a ph of 6.5 in the effluent. The only thing that comes to my mind is that your pumping a huge amount of co2 into the tank. So I would guess that your flow rate is too fast or your co2 bubble count is set too high.