High calcium-Dkh-Magnesium

[Johnnymott]

I'm relatively new to the hobby and brand new to this forum. I've been trying my hand at a mixed reef tank - 46 Gallon Bow front- Hang on the back Refugium- Eshopps 75 wet/dry sump- protein skimmer- hang on overflow. Weekly 5 gallon water changes- weekly testing. My tests this evening were as follows: < 30 Nitrates-
nitrites/ammonia = 0
Temp 79
Salinity 1.0225
PH 8.3
Phosphates 3(I realize they are high - always have been I have no algea issues)
The next three values are high based on published levels
DKH = 14
CALCIUM= 550
MAGNESIUM = 1500
(My calcium and magnesium have always been in those ranges)
Everything I find online suggests calcium and alkalinity have an inverse relationship and suggests stability is more important than some higher levels. Should I be concerned with these levels? Any input would be greatly appreciated

 

[downbeach]

What are you using for test kits? What are you using to test your salinity? What salt mix are you using? Are you using RO/DI water for top off or your salt water?

 

[Johnnymott]

I am using Salifert test kits, RO water for water changes, Red Sea Coral reef Salt, and I have a salinity refractometer which I calibrate every couple months.

 

[downbeach]

Somethings out of whack, RSCP does have elevated levels of those elements, but not at a SG of 1.0225. What are you using to calibrate your refractometer with? If its RO/DI water, get some 35ppt calibration solution, recalibrate the device and recheck your SG.

 

[Johnnymott]

Thank you very much. I will do that and get back to you. I have one more question. I found a great LFS about hour and 15 minutes from my house. If I take a water sample with me and keep it climate controlled would the long drive effect testing?

 

[serbusfish]

Did you mix up the dry salt before you started using it? I made this mistake when I started mixing my own water. You'll need a couple of buckets, tip the salt from one bucket to the other a few times then back into its container (I normally do it 9 or 10 times just to be sure its all nice and mixed).

 

[Johnnymott]

Mix the salt? - I never considered that. Another great piece advice - Thank you

 

[Johnnymott]

Down beach you were absolutely correct! I re-calibrated my refract and my salinity is 1.025! That would explain my high levels? I feel like an idiot! While I am new I am not that new!! I will gradually lower my salinity and recheck. I will post my results. Thanks for all the input

 

[downbeach]

While those numbers are on the high side, they are a little more realistic at that SG. When you're doing the test, you are taking your reading from the end of the black part of the plunger and not the top of the fluid right? Or, as per the insturctions, holding the syinge with the tip facing upward, and reading the end of the black part of the plunger. I wouldn't decrease the SG, its a good number, but I would go to a salt mix that doesn't have those elevated numbers, since your system likely doesn't have enough uptake at this time. If you like the Red Sea product go to the plain salt mix, which has a more appropriate amount of Ca, Mg and Alk for your needs at this time.

 

[dkeller_nc]

Don't (lower your specific gravity). 1.026 is typical for seawater on the reefs that most of our animals come from, and is the value that most of us shoot for. 1.025 is absolutely fine, there's no need to try to adjust to 1.026, and there's an almost certainty that your instrument has a +/- 0.001 or higher uncertainty anyway.

You're correct that alkalinity and calcium have an inverse relationship in that at a certain point, adding more calcium will precipitate some carbonate as calcium carbonate, and vice versa. However, there's a good deal of influence of pH, magnesium concentration and dissolved organic substances on the saturation point of calcium and carbonate (alkalinity, at least for our purposes) in a reef tank's water.

So it's not impossible that you could have a Ca concentration of 550 ppm and an alkalinity of 14 dKH, especially at a magnesium level of 1500 ppm. However, if you're not dosing 2-part Ca and Alk solutions, it's somewhat unlikely that you've a stable concentration of Ca and Alk that high (i.e., based on water changes alone).

Your values, presuming that you don't dose Ca and Alk, suggest a problem with your Alk test kit or the way you're using it. Salifert kits are very well-thought-of, and I'd guess that it's the brand that the majority of serious reefers use on the board, so your kit should be capable of giving you accurate results. The first check is the expiration date, the second is the storage conditions, and the third is analyst technique/interpretation of results.

Presuming your kit is in-date, think about the storage conditions. If you store the kit in a very warm place, you can get degradation of the titrant in that it will become more concentrated (it will actually evaporate through the walls of the plastic bottle - plastic is permeable to water vapor). Assuming your storage conditions are OK, the last thing to check is your interpretation of the colored end-point. That can be a bit difficult to assess, but fortunately Salifert includes a standardization buffer in their kits - simply test the standard solution as you would seawater, and check that your interpretation of the end point gives you a value close to that stated in the package insert.

If your Alk test checks out, then I'd return to your refractometer calibration. One very good way to get a sanity check on your instrument is indeed comparing it with another hobbyist or LFS's determination of a sample of your water. Your water will be more than stable enough over an hour and a half to get a good comparison of its specific gravity, and you could also bring your refractometer to the LFS so that you can check their water and compare it to their readings.