Normal Alkalinity Usage?

[MGarrison]

My tank is about ~300 gallons total volume. It has been cycled for about 4 weeks now. I do not have any corals yet however my alkalinity is dropping by ~.5 dkh everyday resulting in me adding around 100 ml of BRS liquid soda ash. Calcium has moved from 498 (9/17/2020) to current level.

Using Reef Crystals
Other parameters:
Salinity: 35
PH: 8.2 (RedSea test) Planning on implementing Hydros Control 4 when released and didn't want to buy a new Ph probe for my Apex.
Calcium: 450
Magnesium: 1480
Ammonia: 0
Nitrite: 0
Nitrate: 10
Phosphate: 0 (Old Hanna HI713 need to get a better one)
Temp: 77.5 - 78.5

Since I have no corals and cycle is complete (I read that Nitrogen Cycle will consume some ALK) is my current usage expected? I am going through the uglies and have a CUC coming Friday.

Thanks,

 

[Randy Holmes-Farley Verified Community Expert]

Normal for most reef tanks is about 0.5 dKH per day to 3 dKH per day.

What is in the tank?

 

[MGarrison]

2 Clownfish
1 Yellowhead Jawfish
1 Foxface
2 Fighting Conch

No corals yet, CUC will be added on Friday of various snails

 

[Randy Holmes-Farley Verified Community Expert]

2 Clownfish
1 Yellowhead Jawfish
1 Foxface
2 Fighting Conch

No corals yet, CUC will be added on Friday of various snails

Live rock? Sand?

How long have you tracked alk to see the 0.5 dKH per day drop?

 

[MGarrison]

~200 lbs of live rock.. mixed Pukani and CaribSea South Seas Base/Shelf Rock
~150 lbs of CaribSea Aragonite Special Grade Dry Sand
It has been trending that way since Sept 18th.

 

[Randy Holmes-Farley Verified Community Expert]

I'd just keep adding enough alk and calcium to maintain 7 dKH (not more) and then see what happens over an extended period.

 

[MGarrison]

Thanks Randy... I thought 9 dKH was the magic number?

 

[nereefpat]

0.5 dKH per day is reasonable. Coralline growth alone can use more than that in some tanks. Also, the use of about 50ppm Ca is reasonable in that amount of time, and it equates closely enough with alk demand to confirm real usage of both alk and Ca.

Thanks Randy... I thought 9 dKH was the magic number?

7 is closer to natural seawater. Some people run their tanks higher.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks Randy... I thought 9 dKH was the magic number?

7 dKH is fine for corals, and minimizes precipitation of calcium carbonate.

 

[MGarrison]

Thanks.. I am letting it drop down to 7 dKH. Dosed 100ml of BRS liquid soda ash on Wednesday before I posted to bring it back to 9 dKH. Did not dose yesterday or today and was @ 8.06 dKH this morning.