Two Part BRS Dosing, alkalinity requires dosing, calcium stays good? HOW?

[dnguyen1]

Hey guys,

Quick parameters, I have a 75 gallon peninsula w/ a 40g sump
the basics are all stable, 0 nitrite/nitrate
0.04 phosphates
8.4 alk
470 calcium
1350 Mag
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I thought I had everything stable about 5 months ago where I was dosing about 130 ml a day on a 12 dose cycle alternating between alk/calcium.... things stayed stable until they weren't anymore. On a test one day after a couple of months I caught my alk low and calcium way high... meaning off the charts on the Red Sea test.
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anyways, I realized I went too long w/o testing and I tried to recalibrate so I kept an eye out on alkalinity and waited and waited for calcium to drop... now nearly 1.5 months later I'm finding myself to keep alk at 8.4 I'm dosing ~153ml a day and to keep calcium at 470 I'm doing ZERO for calcium. I've been monitoring for the day that I can measure a tangible drop in calcium to start two part but it's not happening.
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I do weekly 10% water changes... can anybody help explain to me why alkalinity will spiral down w/o the 153ml but calcium doesn't need anything to stay good? I have a feeling something's wrong but looking at my tank I'm getting good extension, color and growth on my SPS and my zoas.

Thanks.

 

[dnguyen1]

Bump


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[nereefpat]

The short answer is that water changes are enough to keep your Ca high, but not enough to keep your alk in range.

A lot of folks, when they first start dosing, have to dose alk but not Ca.

The ratio corals use these is about 1dKH to 7 ppmCa. So when your alk drops from 8-7, your Ca may only drop from 480-473ppm. This isn't noticeable on our test kits.

Just keep testing and adjusting your dosing. Since you are getting good color and growth from your sps and zoas, you are doing things right.

Hope that helps.

 

[Silly clownfish]

Theoretically with 2 part, you should be able to dose the same exact amount of both to stay balanced. That has not been the case for me either. I find that my DYI alk is more likely to settle out than my Ca. I suspect that is part of why I does almost twice as much alk as Ca to keep my levels in balance.

 

[dnguyen1]

Ah great to hear guys that this is normal yeah I'm getting decent growth and color so I'm
Happy that it's not an anomaly


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[lionfish300]

Same here more ALK than CA it been for years