Calcium question

[muelpaul]

Hello there,
I have a 180 with 40gallon sump/refuge that has been running for about 2 months, live rock and sand was taken from 2 other tanks.

I have a calcium reactor running since the tank was first setup.
calcium and alk levels were good 400-420 calcium, 4 - 4.5 meq for alk for all but the last week.

I still have 4 meq alk but 350 for calcium, and what is happening is a coating of white calcium like material developing on the front glass. I can clean it off with a razor blade but in less than 24 hours it's back. The snails I have eat right through it as they graze, but it sticks to glass like crazy.

I only have 3 very small frags of sps with mostly soft corals and snails so I am not sure what has made the calcium drop. I have heard about precipitation of calcium when the alk level is to high, but my test kit says 4-6 meq is where it should be.

This is new to me, I never had this problem with my former 46 gallon reef tank that also had the same calcium reactor.

Any advice?

[bertoni]

4 meq/L is about the high end of the recommended zone. What is the pH in the tank? Also, what is the magnesium level?

If the white coating fizzes in vinegar, it's likely calcium carbonate. High pH and low magnesium both would tend to encourage such precipitation.

[muelpaul]

Thanks bertoni, my ph is 8.1, but I don't have a test for magnesium. I did a 15 gallon water change but to no avail.

I retraced my steps to 2 days before this started, I removed an over sized light with a much smaller one, about 50 watts less to 18 watts above the sump/refuge. I noticed some of the macro algae has disappeared and other nuisance algae (brown diatoms) has bloomed .

If the macro algae died, what would be released? would it be something that could explain this?

Pictures from today.

http://i158.photobucket.com/albums/t118/muelpaul/calciumreactor003.jpg

http://i158.photobucket.com/albums/t118/muelpaul/calciumreactor004.jpg

This happened between the time halides came on this morning @ 11:00 and when I got home around 4:30 today. I cleaned the glass with a razor blade last night after all lights were off.

[bertoni]

The macroalgae would release nutrients back into the tank, which would fuel various blooms. There might be a relationship, but I tend to doubt it. Perhaps the magnesium level is low.

Does the film build up only during the day?

[muelpaul]

yes I believe so, I looked this morning and the glass looked clean. Another thing that I noticed, this only happens on the front of the glass, the halides are closer to the front of the tank than the back or sides.

It seems odd that calcium precipitates only with bright light and only to the front glass of the main tank, nowhere else throughout the system.

I will try and find some magnesium supplement locally, but I am sure I will need to order it.

Thanks bertoni.

[bertoni]

If it's only building up in the day, I suspect some sort of algal or microbial issue might be involved. Interesting. Let us know how the tank shapes up.

[muelpaul]

Good news, the calcium like film has not returned! I got the calcium level to 400+ and alk level at 3.5meq/l.

I placed about a 1/4 cup of reef carbon in a filter bag and set it in a high flow area in my sump....not sure if this is what helped but it's the first time I have ever used carbon in a reef tank.

I am still unsure what happened to cause it but I am glad it's gone.
2 of the 3 small sps frags have left started to open up again, funny but my montipora digitata has grown and had full polyp extension through this whole ordeal.

[bertoni]

Sounds good! I have no idea what the problem was, though.