question on dosing water change water

blurry · Feb 28, 2010

I do a water change about every 2 weeks. Usually, I add salt about 2 weeks before I go to use it.

today i tested my pre-mix and th following stood out

ReefCrystals Mix
35ppt
KH 8
Ca 400
mg 1150
PH 8

From the charts i have seen ReefCrystals should have Mg and Ca higher, which wasn't too concerning - but the KH? 4 dKH low?

questions:

I added all the dosing at once - how long should it take for the PH to drop (using recipe #2)?
Is the drop in Dkh due to the water mixing for 2 weeks?
should I mix water 2 days before use instead of 2 weeks?

thanks!

blurry · Feb 28, 2010

I just tested 15 minutes after adding 63ml of KH Recipe #2 and the PH only went up .2 - does that sound right?

RBursek · Feb 28, 2010

No that does not sound right for the new RC at 35ppm, check your refactometer, I just mixed up a batch and as usual it was 520Ca 1400Mg and 13 Alk and it was mixed last weekend and added yesterday. You donot need to let it sit/mix for more then 24hrs at the most. Here is a calculator for your Alk. Donot worry about the PH, test that after the water change, there is 2 different #2 recipes 1 will lower PH and the other will raise it.
Reef Chemistry Calculator

blurry · Feb 28, 2010

just tested the refractometer against pinpoint 35 fluid and i'm reading 35.5 or so - off a tad, but not enough for that kind of alkalinity difference...

RBursek · Feb 28, 2010

WHat is your tank Alk/? If close to 8 I would go with it and then adjust the Alk of the tank water after the change accordingly.

blurry · Feb 28, 2010

tank is at 10. I dosed the preMix to get it up to 10 and did the water change. I was surprised to see the alkalinity so low on the pre-mix.

What causes alkalinity to drop in a tank? could a similar event be happening to the pre-mix?

lazyreefer · Mar 1, 2010

I had low numbers of 360, 1050, and 8 out of a recent bag of Reef Crystals. There are four bags in a 200 gallon box and I work out of a single bag at a time. Hadn't really tested the fresh SW before but I'm gonna start doing it regularly. Actually, I'm gonna go buy a bucket of Coralife which supposedly has higher numbers than RC and see how that works out.

RBursek · Mar 1, 2010

Corals use Alk just like they use Ca and Mg just at a different rate.

wicked demon · Mar 1, 2010

The Ph of the water you are starting with will effect the Kh of the mixed water, try aerating the RO water for a while prior to mixing the salt in.

wicked demon · Mar 1, 2010

RBursek said:
Corals use Alk just like they use Ca and Mg just at a different rate.

If I am not mistaken they use this ratio;
Calcium-1:Magnesium-1:carbonate-2(bicarbonate)

RBursek · Mar 1, 2010

If he has CO2 in the house being winter time aerating it will lower the PH unless he can use outside air to aerate with.

blurry · Mar 1, 2010

wow, once again you guys are feeding me good information! I'm going to do a controlled test on the mix later this week. For now the tank is doing well

I didn't realize corals consume alkalinity - thanks!

RBursek · Mar 2, 2010

And the ratio that was posted here is not correct, different corals use it at a different ratio, and Mg is used far less the the other 2 that is why when you get Mg levels where they belong they stay there with out much if any dosing just with water changes unless the salt you use is very low in Mg.