Calcium absorption rates

So I have started to notice that my reef is starting to deplete in calcium over the last week. 10 days ago my cal was @ 420 - ph was at 8.3

Tested yesterday and my cal was @ 310 and PH 7.9 (tested both 3x) (also did a 5 gal wc on Friday)

I have started a regiment of cal dosing and a trace element dosing - Hopefully to start bringing up my cal levels over the next 5 to 7 days.

I was very surprised that the cal dropped so fast but my mag stayed even.

I added 2 weeks ago a bubble coral and fox coral - do these type of corals absorb calcium faster then other lps? Has anyone come across an article on lps cacium absorption rates?

What could I have done different? adding two lps at the same time a bad idea?

 

interesting observation!!!

And this is in a 75 gallon tank? Seems like quite a calcium demand.

A bump for someone more knowledgeable in aquatic chem than I!

 

Yes it is a 75 gal - I might have a heavily stocked lps - I didn't think it would be an issue - but looks like I have created my own problem

These are the LPS: torch coral (2 1/2 heads) 10cm by 10cm bubble coral - getting larger open brain coral - 3 head fox coral - small favia and a fair size sun coral.

 

I am one of those chemistry challenged people. Our wonderful mod Steve Wright always make it sound so clear.

So my own observations of my tank: I try to maintain my ca at 450, but the uptake is really rapid in my tank by day 3 after dosing, it will drop to around 350. I have a lot of coralline algae and growing harding corals. As the tank grows and ages the faster the drop have become. I tried to be happy at 350ppm and everything did well but at 450 everything really grows much better.

The discrepancy in the alk is not as noticeable. I understand the ratio portion of it and that ions will always act in a fairly predictable manner. But the alk level seems to remain more stable.

I have gone from dosing every 3 days to dosing everyday now and also increased the amount dosed daily.

Generalizations can probably be made regarding uptake, but every tank is going to be have very different rates based on over all chemistry of the tank and the types of corals and inverts it contains.

When parameters look off, try another test kit to verify the values. Having a nano makes dosing easier, I can only imagine the amount of dosing products larger systems go through.

 

IMO, for the corals listed, that is an oddly high Ca absorption rate.

What is your Mg reading? Wondering if it's not high enough to keep your Ca stable(??).

 

Also, I lose about 10 points a day but I have quite a bit more stony coral than you listed...

Tank size isn't relevant. Coral load is.

 

+1 on 10ppm drop per day over 10 days seeming rather high for a tank that has no SPS or Clams listed in the signature

I have a tank containing almost 30 SPS corals of varying sizes and approximately a dozen LPS corals (brains, lobos, wellsos etc)

Im only compensating for about 6ppm calcium per day at present and just under 0.5 DKH

whilst in theory the utilisation rate of calcium to carbonate alkalinity is often stated as 20 parts calcium to 1 DKH
The reality is that

A - there are other reason for a dropping DKH other than coral intake (maintaining PH )
thus in many tanks there is a greater demand above and beyond the 20 - 1 ratio for carbonates

B - corals can use Magnesium and in fact strontium as an alternative to calcium or in other words you dont always get a drop of 20ppm calcium with every 1 DKH drop ( as maybe 16 Calcium are used along with 3 magnesium and 1 strontium - just an example, I have no idea of what the actuals ratios are, or even if they can be measured )

Randy once stated that due to the combined effects of alternative/ substitute ions that can be used by corals and coraline combined with the carbonates being utilised to stablise PH , its actually not rare to find that in many cases as little as 6- 8 ppm calcium can be used by corals in the same period that DKH drops by 1


so in summary

+1 on those that indicate you want a second opinion on the test results

and that adding 2 LPS corals into a 75 gallon tank, would not explain a sudden demand increase of 10ppm Calcium each day

are you dosing KH buffer?
as indicated above - it may be that if you are, you are dosing that and then knocking your calcium level down?

because the 20 - 1 ratio is more factual when dealing with precipitation
in that if you dont have a magnesium level capable of supporting all the ions in solution
then for every degree of DKH you add, you can lose up to 20ppm Calcium

you Mag level is key to finding out if thats the case

Steve

 

Thanks Steve, Perehil and Corilline

I was/am using instant ocean reef accelerator and have now added (last night) instant ocean calcium boaster.
My Mag is @ 1200.

I was/am planning to add calcium everyday for the next week to see if I can increase ph and calcium to were it is acceptable. Is this the right path? or should I do a wc first if so what % would you suggest?

 

Your Mg is too low and that's why you are seeing Ca drops.

Raise your Mg to somewhere at 1350-1500 and keep it stable. THEN worry about your Ca reading.

 

Reef Aquarium Water Parameters by Randy Holmes-Farley - Reefkeeping.com

welcome

1stly - your magnesium is on the low side and needs to be increased to 1250 - 1350
or slighty over is also OK IMO (currently maintainnng 1440 in my set up)

2ndly - Reef Accelerator is one of those all in one formulas which means if your levels are OK to start with, and your demand is normal across all parameters, then it might work for you (might) although I have not tested this product (I will if I see it) my suspicion is that it probably adds more of 1 thing than you need, whilst at the same time adds less of another thing you need - hence your levels are out of whack due to using this product

if it where me
I would bring my Magnesium up to 1350 (take at least 2 days to raise the 150ppm you need) using a product with both Mag Sulfate and Mag Chloride (balanced) such as Magnession by Brightwell (there are others thats just an example)
or for a more cost effective method check out the BRS Mag supplements

once you have your mag at 1350
then you can look at increasing your calcium to 380 - 450
and then look at maintaining a DKH level between 7 - 11

again using product designed to increase those individual ions, rather than a product thats supposed to maintain both (that way you can address each level individually when you need to, which you cannot do with a product like accelerator )

you need to get that mag level to a point where it can accomodate the other ions in solution otherwise , you add A and B falls out

Steve