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Old 04-23-2010, 02:16 AM   #1
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pH dropped and dKH after PWC

Hello all,
I just got a 200g box of reef crystals since I was out. I just did a PWC and tested my parameters and found the pH and dKH to have dropped significantly.

My pH is usually around 8.3 and my dKH is usually around 8-9dKH. After the PWC, my pH is now 7.8 and dKH is at 7dKH. Calcium is high at 520ppm.

I dont understand what has happend? I thought PWC would improve paramters rather than hurt them.

My tank has been up and running 11 months.

I added some dKH buffer, but from what I understand, that will only be a bandaid. I dont dose anything else. My thinking is Magnesium is low? I guess I ought to get a test for magnesium and find out? I was hoping that PWC would prevent me from having to dose chemicals. (Only a couple hard corals).

Thanks,
Matt
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Old 04-23-2010, 08:36 AM   #2
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I would think it's a testing error. A fresh mix of Reef Crystals normally has an alk level of about 13 dKH. I don't see how a pwc would drop your alk from 8-9 dKH to 7 when you added water that's 13 dKH.

Did you test your fresh mix? How long did you let it mix before using it?

Why do you think your mag is low? It should be in the 1440 range with Reef Crystals.
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Old 04-23-2010, 02:39 PM   #3
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I didn't think they made 200g boxes of reef crystals. I use reef crystals but in the bucket. I've never had a problem because of water changes. Are you sure you added the correct amount of salt? If you are using a new kind of salt it may require a different amount to be added to the water. What's your salinity at?
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Old 04-23-2010, 02:56 PM   #4
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Along with jaybird's question about salinity, how much of a water change are we talking about here? 10%? 20%? 80%?

I've had some inconsistency lately with Reef Crystals' parameters, but with smallish sized water changes I wouldn't expect to see much of a change with just one water change. Unless the new saltwater was mixed to a lot lower salinity.
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Old 04-23-2010, 03:27 PM   #5
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Quote:
Originally Posted by Jaybird View Post
I didn't think they made 200g boxes of reef crystals. I use reef crystals but in the bucket.
The 200g boxes (4 50g bags) are the "new forumla" Reef Crystals. Depending on where you got your bucket, it may be old stock. I'm not sure if the new formula is also in buckets.
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Old 04-23-2010, 04:10 PM   #6
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The reformulated RC is in the buckets too and the design on the bucket is different than it used to be. This is what the new stuff looks like...

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Old 04-23-2010, 06:15 PM   #7
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Hello all,
I didnt test the fresh salt water before putting using it. I just did a 10% water change.

An hour after adding the buffer, my parameters were "more like it". pH was back to 8.3, dKH was at 9, but calcium still around 520ppm. Salinity was at 1.025. I will test again in a little bit to see how things are.
I thought magnesium low since both pH and alkalinity were low while calcium was high.
EDIT: Tested a newly made batch of salt water. Salinity: 1.025, dKH : 13, pH : 7.8
Matt
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Old 04-23-2010, 06:48 PM   #8
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Even if the new water was really off on parameters, I can't imagine things changing that much with just a 10% change. Must've been testing issues or one of those weird things that we can never explain.

I'm guessing your calcium is that high because you've added something like PurpleUp, or some TurboCalcium, or something? Normally, you want your magnesium levels to be about 3x your calcium levels. But in your case, I doubt they are, so I imagine they'd appear to be "low" with respect to calcium. However, I'd be more apt to think that your calcium levels are just too high.

Whenever I start a new bucket of salt, I always test the first few mixings for pH, alkalinity, and calcium... before they go in the tank. That way I know for sure what it is I'm putting in.
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Old 04-23-2010, 07:01 PM   #9
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Hello,
I used to dose calcium with Seachem calcium+magnesium, but stopped that a few weeks back. Since then, there have been a couple of 10% PWC that should have brought down the calcium. Could it just be the Reef Crystals keeping the calcium high?

Is 520ppm calcium going to hurt anything? I have some LPS and SPS (acropora and montipora) as well as shrooms and other soft corals.

Thanks,
MAtt
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Old 04-24-2010, 01:24 AM   #10
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Quote:
Originally Posted by mrg02d View Post
Hello,
I used to dose calcium with Seachem calcium+magnesium, but stopped that a few weeks back. Since then, there have been a couple of 10% PWC that should have brought down the calcium. Could it just be the Reef Crystals keeping the calcium high?
Not sure where your calcium started out at, but lets just say it was 540. After a 10% PWC with Reef Crystals (let's assume 420ppm calcium with that), that would drop it to 530ppm. Another 10% change drops it to 520ppm. You see where I'm going... with 10% changes it takes a while to really change certain parameters. Eventually, your tank calcium levels will be closer to that of your Reef Crystals, which I'm guessing will be in the low to mid 400s.

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Is 520ppm calcium going to hurt anything? I have some LPS and SPS (acropora and montipora) as well as shrooms and other soft corals.
It's not going to hurt anything, as far as I know. The big drawback is that it is difficult to maintain higher alkalinity levels (as in higher in the 8-12 dKH range) with higher calcium levels. You can have one or the other high, but not both at the same time. Personally, I'd just let it drift lower on its own through coral consuming it and PWCs with Reef Crystals.
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