Alk won't go above 5.5

[5ft24]

Subject says it all. I moved my tank back in July across town. Due to cyano, I took the time it was torn down to replace the sand and scrub the rock. Used 60 pounds of fresh Fiji Pink, and scrubbed all my rock with a stiff brush 3 times in fresh saltwater every time.
It's a 55g sumpless system.
All reassembled, probably 45 gallons new water, made with RO/DI. Checked params after a week, nitrates at 80, salinity 1.023, CA at 410, phosphates at <.025. dKh 5.5. Mixed 10 gallons of water. After 24 hours the 10g was 1.023, CA 410, Nitrates and Phosphates 0, dKh 9
Did a 10g water change. After 1 hour, checked dKh and it was 7.
The next day, back to 5.5
Thought my test kit may have been funky, so took the water to the LFS. Same reading.
Thinking there may be High CO2 in the house, I ran the skimmers air intake out the window. Next day, still 5.5. Did another 10g water change, and same thing. dKh came up to 7 then dropped to 5.5 within 24 hours.
Only coral is 2 frags of Zoas.
So, I decide to dose sodium Carbonate. Followed the calculator for dosage amounts. Dosing 1tbsp/day, it goes up to 7 with a check after an hour, and again, within 24hours drops back to 5.5... WTF?
Anyone else fought this?
55g no sump, reef octo new style HB90 skimmer, ecobak pellets, dual powerheads, and an emperor 400 HOB filter without cartridges used for water movement.
2 48" actinic and 2 12k t5's
300W heater, tank stays at 78 +- 0.2


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[1guydude]

Is your issue with ph or alk/dkh?
The skimmer fresh oxygen air intake would be mostly to stabilize your ph swing and oxygen levels.
Are your pellets tumbing in a reactor?
D

 

[5ft24]

Alk. Pellets are tumbling good, and I vented the skimmer intake to the window just to make sure there wasn't a buildup of CO2 in the house causing issues. Before I moved the tank, my dKh would stay 8-8.5

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[1guydude]

Well i would say buffer and or dose than large scale water change followed by a buffer or dose. Is your coral or coraline algae eating it all up? Pix?!
Im by no means an expert.
D

 

[5ft24]

Only corals are 2 frag plugs of Zoa's. As far as coralline, I haven't had any new growth of it in a while. Though I do have to scrub the glass every day to keep the hard green algae off the glass

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[spieszak]

If you mg isn't right, alk and cal will bond and neither will rise.

 

[tike]

Running a sand bed? If so, are you noticing any clumping of the sand?

 

[tike]

Also, what's the ph of the tank.....both day and night time?

 

[5ft24]

Yep. 60 pounds of Fiji pink in a 55gal
No clumping. Will check PH

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[5ft24]

Is there any way to reduce mag short of major water changes, and how much is it safe to bring down at once without causing other issues?

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[spieszak]

What is your magnesium registering at?

 

[5ft24]

According to the LFS, 1500.
I need to get my own test kit though.

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[1guydude]

1500 isnt terrible imo...
D

 

[spieszak]

mine is pretty steady at 1350 or so, i wouldn't be terribly worried about 1500 either...

 

[spieszak]

are you dosing anything for calcium? I saw this a long time ago when my calcium was testing right, but it was way to high. If you are, try skipping it for a week and restesting. Your tank isn't using it anyway with alk that low...

 

[5ft24]

Only thing I am dosing is Calcium Carbonate to try and boost the Alk

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[spieszak]

How often? Calcium Carbonate is balanced... its much harder to raise numbers with it, its much easier to maintain numbers with it.
Guessing since its balanced, you are raising both, but your calcium is right so then you can't reach a balance...

try raising it with baking soda
calculator here
http://reef.diesyst.com/chemcalc/chemcalc.html

I wouldn't go more than 1 dkh a day, and I'd back of the kalkwasser until alk was right.. Then I'd go back to kalk (in top off)

 

[Blue Lip]

Raise your salinity to 1.025

 

[5ft24]

Why?
After its been mixed to 1.023, I test it and alk is 8.5-9. I've never run any of my tanks 1.025.
And in 10+ years of reefing, have never had an issue that dosing didn't help, or where alk dropped over several days, even with over $5k in SPS in the tank
This tank has probably 20 heads of Zoa's.

Raise your salinity to 1.025

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[NanaReefer]

Yep. 60 pounds of Fiji pink in a 55gal
No clumping. Will check PH

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Check below the surface of your SB for clumping. I'm using the same substrate as you and this is what I discovered under the surface of mine!!