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Low alkalinity normal calcium

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I am wondering why my tank would have low alkalinity but normal calcium levels? 

My alkalinity is currently 6.5 and my calcium is 440. What’s the best way to fix this? Water changes? I’ve been reading about calcium and alkalinity online but I’m still somewhat confused with their relationship and so I’m not sure how to address this issue. 08634CE5-864B-469A-8034-9E47DCEEB7A6.thumb.jpeg.5f12ca034a48ce3ca5d501a0e765bc4e.jpeg

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Yea no matter what my tank seems to use more alk than cal even though that's not "possible".. anyways that is quite of bit off .. how often do you do w.c. and do you test your mixed saltwater before you add it to the tank. I have had bad batches of salt that come with really low alk.. what ever you do dont do anything fast , I crashed a tank once tring to raise my alk back up after I did a big wc with low alk... 

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just dose the alk. portion of 2-part by itself once or twice.  monitor....and slowly get it up to @ 8.5-8.9


or just dose both...i dont really care what my CA is at unless its over 500.  I dont overthink or stress on CA.  trying to understand that relationship in any great detail has never done me any good.  I keep my alk. at 8.0-9 and I dont care what the CA is unless its under 400 or over 500


if you dont have a 2 part solution, dont mess with the BRS stuff...just get some Bionic.


Now, DO NOT SPIKE the alk.  just get it up to around 8+ over several days.  if the CA goes up too, so be it...but if I were you'd id do one day with Alk. only then the next day with both...


Slowly raise it. you can let Alk. drop but you cannot raise it quickly or bad things happen.


I'd also get a good salt mix, and do weekly or once every other week changes....I like Fritz RPM as it mixes to the 8.5 that I want.


long story short you want a good mix that after you TEST mixes to 1.026 at 8.0 or so.


also a good time to invest in a Hanna Dkh checker

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Hi Hannah. I have been reading your journal, and felt I should add my two cents worth (I am also establishing an EVO 13.5, started on 4/1/2019, so I have been following a lot of these builds here).


In the past week, you had a dead emerald and hermit in your tank, and added at least one other invertebrate, the feather duster, plus a goby after those deaths. I am not sure about your tank born on date, but it seems to be a rather young tank. The reason I bring up the other things I got from reading your journal isn't to say that you are going too fast, but to illustrate that the entire eco system you are building is complex, and the parts are so intertwined. And was it in your journal or another post from you where your were thinking about changing your salt? And unless you traded in a cardinal, you now have 4 fish in the tank. How is your ammonia, nitrite and nitrates?


The corals you have added over the last few weeks are starting to consume Ca and other stuff that leads us to testing and dosing to match the consumption rate of our tank. The one thing I have learned here on this website over the years is to not chase a single parameter. You are getting good advice, but it may be advice based on some assumptions.


Yes, the alk is low, but what about other params? Ca, Mg ok? What about phosphates and PH? What are the target params from your saltwater mix? The relationship is complex I know, still trying to wrap my head around it myself. And the invert deaths, if it wasn't just the end of their life span, what other things could have contributed to it?


And I think you could benefit from slowing down. The other incredibly useful advice I have gotten from here is that this hobby rewards patience. It is tough, I have one coral too many in my tank as it is, and I started with cured live rock, and sand from an established tank. I only have some hairy mushrooms, and one unidentified sps (probably cyphastrae). I really don't count the hairy shrooms as a coral, it is mainly a weed that I would be hard pressed to kill. Plus my clowns loved them in my EVO 5, I wanted to give them something familiar in their new home. 


Your tank is looking great, I hope to see more of it in the future.


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