High Demand for Alk/Ca

[sierra112]

I have a 75g mixed reef: 1-5" maxima,3-LPS, 1-SPS, numerous soft corals, and a 20g fuge with a DSB and Cheato. My concern is that I'm having to add a DAILY dose of 4tps Reef Builder, and 4.5tps of Dry CA to meet the demands of the tank. I also drip Kalk opposite of my light cycle to replace evaporation (1g a day). I perform water changes weekly w/ RO water that is first airated (24hrs), then buffered (for 24hrs). My PH fluctuates between 8.0-8.24(PH monitor). Other parameters for my tank are:
CA - 375
Alk- 8.4dkh
Nitrates - 0
Ammonia- 0
Nitrites- 0
SG- 1.025
Temp- 81-82
mg- 1150

I'm just curious if this daily dosage is normal for anyone else.

[Randy Holmes-Farley]

It is "normal' for a typical tank to add about 1-2.5% of the tank volume in sturated limewater. You are adding just over 1 (if that is saturated with 2 teaspoons per freshwater gallon) and then are adding about twice that amount again (assuming that you mean teaspoon by tps). That's a bit on the high side, but not outragous.

Are you getting a lot of CaCO3 precipitation on your pumps or heater?

Is the coralline algae growing fast?

If the magnesium levels were sub par, that could lead to excessive demand by allowing more abiotic precipitation.

[sierra112]

I dose 2 teaspoons/gal of kalk nightly. My magnesium has remained fairly consistant at 1100-1200. Coralline growth was agressive until recently. It hasn't receded, only showing less growth. I did have a layer of precipitation over my heater and over the top of my skimmer pump a few weeks ago. Both were removed and cleaned...I checked my heater just now...It's back, and covering 3/4 of the heater. Where to now?

[Randy Holmes-Farley]

I'd suggest getting a magnesium supplement and raising the magnesium to about 1300 ppm. That may reduce the abiotic precipitation.


This article and calculator will help:


Magnesium
http://www.advancedaquarist.com/issues/oct2003/chem.htm


Reef Chemicals Calculator
http://home.comcast.net/~jdieck1/chem_calc3.html