Low Calcium Level

jfenton954 · Mar 13, 2012

I have a 75g reef tank with 2x 250w mh, 4x 54w actinic t5s lights. Around 175 lbs of coraline covered live rock. I've noticed that there are white spots all over the tank so I googled it. I read about low Alk levels so I tested it, it's at 8. Then I read about low calcium levels so I tested it, it was at 320

. I do a 10% weekly water change with Tropic Marin Pro. What could cause calcium levels to drop that fast?

revhtree · Mar 13, 2012

What is the calcium level right after your water change? Also is that the only way you are maintaining the levels?

donfishy · Mar 13, 2012

what are your alk and pH levels? all three are intertwined, and I would guess that if your Cal is low, your alk is high might want to check

jfenton954 · Mar 14, 2012

I haven't check after water change but I will check then also. My Alk is where it should be at 8-9. Ph is low..... It bounces between 7.60 to 7.95.

Glenn · Mar 15, 2012

jfenton954 said:
What could cause calcium levels to drop that fast?

How much coral do you have in the aquarium? As corals grow, they use calcium from the water.

How often do you add top-off water to the tank? Is it (RO) water only? Try adding kalkwasser as your replacement water with each top-off.
.. Each morning, I add about 1.5-2 gallons of top-off. The first gallon is kalkwasser that I made the day before.

mallorieGgator · Mar 16, 2012

Are you using Ro/Di water? If not, then your calcium can precipitate out and your levels will say pretty low.

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mcarroll · Mar 16, 2012

jfenton954 said:
I have a 75g reef tank with 2x 250w mh, 4x 54w actinic t5s lights. Around 175 lbs of coraline covered live rock. I've noticed that there are white spots all over the tank so I googled it. I read about low Alk levels so I tested it, it's at 8. Then I read about low calcium levels so I tested it, it was at 320 . I do a 10% weekly water change with Tropic Marin Pro. What could cause calcium levels to drop that fast?

First, I would recommend switching salt. Topic Marin's Pro Reef is what I'd call a "specialty blend" due to how its Ca/Alk/Mg are weirdly balanced. I've seen lots of people have chemistry issues after trying to deal with this salt without being prepared. (It's not impossible to use, but not at all recommended for newbies.) If you're hung up on the Tropic Marin brand, then switch to their regular salt which is normally balanced. If not, I'd have to recommend Instant Ocean or Reef Crystals.

-Matt

P.S. You don't really have 175 lbs of live rock in there do you? About 70 lbs would be plenty if your intention is to grow coral.

reeffirstaid · Mar 16, 2012

I agree with mcarroll. I would recommend Brightwell Aquatics Neo Marine. It is specially formulated for the reef environment and helps maintain proper calcium/alk levels with every water change. Calcium and Alk typically walk hand in hand. Another helpful thing can be supplementing with a calcium and alkalinity buffer. I like the one that aqua C makes. You use a part A and B solution to help buffer and maintain proper calcium levels and alkalinity levels. Although personally if your ph is alright (8.1-8.3) and your specific density is alright (1.025-1.027) I wouldn't worry about it. Continuity often proves more important then specific values in reef aquaria. 320 really isn't that low and an alk of 8 isn't off by much. If you could hold that balance with the proper ph you should be ok.

REEFKEEPER10 · Mar 16, 2012

What is your magnesium levels.

jfenton954 · Mar 16, 2012

Don't have a magnesium test yet....... Also I didn't know there was a special way to add salt to your tank.....?? I mean I'm not that new to reefing I have a refractometer. This is a new experience so I asked about it. An yes there is 175lbs of rock (biological filtration)

smadascott · Mar 17, 2012

I think that what is happening is your aquarium in consuming more calcium then you are adding with your water changes. Over time the amount of calcium and other compounds that you aquarium uses will increase at a steady rate (if your aquarium is healthy). I have logged data on this subject that shows this trend over years at a time.

It sounds like you do your water changes after a set period of time, which is good! If you really want to be exact then you can determine how many ppm's of Ca you are adding with the water change and then calc how many more ppm's(mg/L) are needed to get it to where you want the value to be.

example:

100 gallon aquarium; change 10 gallons a week
convert to liters --> 3.785L * 100= 378.5L and 37.85L changed per week

salt mix says the calcium level is 420ppm when mixed

1ppm= 1mg/L so 420mg/L then amount per water change 420mg/L*37.85L=15897mg/L/water change

If your Ca level stays constant when testing before each water change then your aquarium is using the same amount of calcium as you are adding over you set period of time. If the Ca level is below the tested value of your last water change then your aquarium used more calcium then you added with your last water change.

To raise your Ca you would determine the difference between your tested value and your desired value then add that much calcium to your water change.

example:

tested @ 390ppm; desired is 420ppm; 420-390=30ppm (mg/L) ; 378.5L*30ppm=11355mg(11.355g) of Ca you need to add to your water change

The amount of calcium you add will have a direct correlation with the amount of KH buffer you add and both these values should increase over time