Noob dosing questions

[b4tn]

My test kits and 2 part solutions came in yesterday. Since right now I only have 2 LPS and a pair of Zoas doing 10 gallon water changes weekly, I honestly expected my levels to be pretty close to the recommended. Here is my initial test

Calcium 325 ppm
Alkalinity 5.3 Dkh
Magnesium 1080 PPM

Since I just did a water change Saturday I was a little surprised that levels where that low. I am using standard instant Ocean salt.

My question is, how to factor in water changes with Dosing? I would think that since doing a water change will raise the levels that would affect the daily dosing amount. My calculated water volume is about 80 gallons so I plan on dialing back water changes to 5 gallons a week. I have the BRS 2 part kit and it is very straight forward but nothing is mentioned about the the additional variable of weekly water changes when calculating your daily amount.

 

[BfishLpond78]

Those numbers are pretty low out of the bag, it all depends on how crazy you want to get with your dosing and water changes. If you really wanted, you could mix new saltwater and test it...then dose additives to bring it up to the levels of your liking. But if your plan is to move to 5 gallon WC's I don't see that as adding a huge impact to your dosing regimen. Just make sure to test regularly to note any changes and adjust dosing accordingly.

 

[b4tn]

I would have to look at the bucket but I am guessing because I am using the standard Instant Ocean and not using Reef Crystals. Since it was my first time ever using the RedSea test kits, some of that could also be due to user error so I will probably test one more time before calculating an amount.

 

[redfishbluefish]

Your calcium number is in the ballpark for IO salt with the alk and mag numbers lower than expected. Two questions:

What is the salinity of your tank (and what do you use to measure salinity)?
What test kits are you using?

 

[b4tn]

Salinity I keep at 1.026 and it stays consistent by using at ATO system. I am using Refractometer I also got from BRS to measure.

I am using RedSea test kits.

 

[b4tn]

One thing I do think is strange is my PH is always pretty low, below 8 at night and below 8.1 during the day. I just attributed it to being a new tank but isn't alkalinity directly tied to PH?

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, I do not believe that the magnesium number can be accurate if the salinity is accurate. One of the two is probably in error, and unless the tank has been set up for a long time, I expect it is salinity.

How are you measuring it?

Don't worry about the pH. It is fine.

 

[b4tn]

I will run all the tests again tonight. Like I said it was my first time using a test kit other than the add 5 drops and wait for 5 minutes kits. I am pretty confident salinity is good since I use a refractometer that I test for calibration weekly before water changes.

 

[Randy Holmes-Farley Verified Community Expert]

I will run all the tests again tonight. Like I said it was my first time using a test kit other than the add 5 drops and wait for 5 minutes kits. I am pretty confident salinity is good since I use a refractometer that I test for calibration weekly before water changes.

How do you calibrate the refractometer?

 

[b4tn]

I bought a 1.026 solution from BRS http://www.bulkreefsupply.com/aqua-craft-refractometer-calibration-fluid.html. I keep the fluid and the refractometer near the sump area so its close to the same temp as the tank water and let it sit on the refractometer for about 30 seconds or so before reading it.

 

[beaslbob]

IMHO measure pH just before lights out.

I refugium with growing macro algae will not only raise the pH but consume ammonia/nitrates, phosphates and return oxygen.

I would test just after a water change.

FWIW I had much lower magnesium (using instant ocean) than your values and had to do a one time massive adjustment. Like pounds of Epson salts/magnesium chloride. After the adjustment the diy two part kept it up over 1300 or so.

I would just do the diy two part. Once you do that initial adjustment, it is extremely easy to test for and dose. Plus it is inexpensive and effective as well.

still just my .02

 

[Lenny_S]

I really don't think you need to take water changes into account at all. Regardless of volume lets say you do a 20% water change (pretty big). And your current calcium is 325, and the calcium of the water added is 425. That is really only a difference of 100 within that 20%. So once that is diluted within the other 80% that wasn't changed, it would only increase the calcium of the total volume by 20. That's pretty negligible and probably could be considered within the margin of error for most calcium tests. I'd say the same goes for magnesium. A 10% water changes would be even less impact, a calcium difference of 10 in this case.

 

[Randy Holmes-Farley Verified Community Expert]

I bought a 1.026 solution from BRS http://www.bulkreefsupply.com/aqua-craft-refractometer-calibration-fluid.html. I keep the fluid and the refractometer near the sump area so its close to the same temp as the tank water and let it sit on the refractometer for about 30 seconds or so before reading it.

OK, that sounds good.

 

[b4tn]

I really don't think you need to take water changes into account at all. Regardless of volume lets say you do a 20% water change (pretty big). And your current calcium is 325, and the calcium of the water added is 425. That is really only a difference of 100 within that 20%. So once that is diluted within the other 80% that wasn't changed, it would only increase the calcium of the total volume by 20. That's pretty negligible and probably could be considered within the margin of error for most calcium tests. I'd say the same goes for magnesium. A 10% water changes would be even less impact, a calcium difference of 10 in this case.

Lenny, you make a very good point. I never sat down and did the math but when you do it really is negligible.