Help with BRS 2-Part

[jackers]

I have an 85 gallon reef, 15 gallon sump, and about 80 lbs of live rock. I am figuring my total volume is around 85 gallons.

I use Seachem salt and have been doing about 18 gallon water changes every weekend.

I have a bunch of zoas, duncans, GSP, many frags of favia, some chalices, some leptoseris, monti's, etc. So mostly LPS/Softies.

My parameters after a water change are around the following:
420 Ca (elos)
7-8 Kh (salifert)
1350 Mg (elos)

Ok, I have always heard you have to dose equal parts calcium and alkalinity. Come Thursday nights, my parameters are right around here:
420 Ca
5.9 Kh
1350 Mg

How is my alkalinity dropping yet my calcium is staying put? I have been dosing only alkalinity to bring my levels back up (over a few day period) but can I start dripping alkalinity but not calcium? I have a Neptune Apex with the BRS dosing pumps, so I know I can really dial in my dosing.

Any help is appreciated.

 

[ritter6788]

You can dose alk without calcium. It is used in proportion but alk falls below acceptable levels before calcium. Calcium is used only 7ppm to 1 dkh alk (20ppm per meq/l alk) so a calcium drop may not be as noticeable until more alk is being consumed.

 

[ReefPops]

I've had the same problem and would dose just the alkalinity. Personally I'm not sure what the reason is for the difference, but had no problem dosing just the one. Just make sure you monitor levels so you don't do too much of one and not the other.

 

[jackers]

Thanks guys. I will start dosing after this weekends water change. I will start slow and do my checks every other day till I know my tanks usage rate.

 

[ritter6788]

Good call. Frequent testing is important. Alk is the most important to keep stable. If you can invest in a dosing pump to keep it stable it will be worth it in the long run. Especially keeping hard corals and clams.

 

[jackers]

Good call. Frequent testing is important. Alk is the most important to keep stable. If you can invest in a dosing pump to keep it stable it will be worth it in the long run. Especially keeping hard corals and clams.

Good point. I have the BRS dosing pumps and a Neptune controller.

 

[fjpod]

I also have trouble keeping my alk up. Ca stays fine. So I add alk with my topoff daily and my Ca gets replenished with my weekly water change. I change about 2 1/2 gal per week on a 14 Biocube.