When people talk about 'X degres KH consumption' why does this not refererence 'per X [measurement system] of water?'

[autologyx]

I'll risk an obvious answer to this.. if its a foolish question then forgive me!

You often hear people say 'I consume X degrees of KH per day' by which I take it to mean 'If I don't dose (whatever they are dosing) then their display inhabitants consume Carbonate sufficient to drop the measured KH in that display by 1 degree in a 24 hour period. So far so good.

But what is that actually measuring in terms of dosing? By this I mean that without a volume to reference that '1 degree drop' is simply specifying the impact of consumption of an unknown amount of available Carbonate hardness per X volume of water'

What is X ? per litre, per gallon?

Anyway, It's been on my mind to do the calculations for a while to see what I'm consuming having switched from a Calcium reactor to DIY All for Reef using CarboCalcium (Calcium formate) on all my displays.

I'm using a GHL KH Director which is well set-up and properly calibrated to to ensure that, irrespective I can demonstrate that over an extended period, alkalinity remains constant (the display in question runs around 9.2 dKH) and were I to stop dosing the drop would indeed be around 1dKH for the 260 litres the display has including sump (no colonies just frags in this display). The GHL isn't in active mode (it doesn't control the dosing pump) which instead is set to deliver around 3,000ml per month of a mix that has 210grams of CarboCalcium powder dissolved in it.

I geared myself up to do the calculations the long way around and got half way through working out relative masses for each of the elements in Calcium Formate (which is what CarboCalcium is before realising that TropicMarin helpfully give values:

They state that for each 100g of CarboCalcium powder you derive 30g of Calcium and 4,000 °dKH

So... Based on consumption of the mix I run that works out at 2.1g of Calcium per day and 280 °dKH which is about 1.08 °dH per-litre per day in this display.

That number of 1.08 brings me back to the question...

When people talk about consumption (X drop per day), is that the right way to express it?

Surely without the unit of volume, all that number can tell you is that -for that display, relative dKH drops by 1 degree i.e. showing what the impact of NOT adding any supplemental Calcium Carbonate would have, NOT what you are actually needing to add for a given volume of water to maintain it.

Put another way - if I was adding 460 grams (twice as much) to maintain a consistent level then my consumption would be 4g of Calcium and 2dKH per litre per day.. I could still have a drop of 1dKH per day (or 5) for the given volume of water depending on what the stocking level was..

Its late at night here in the UK, but I'm think the math is correct. What I can't get my head around is the way it should be expressed whether we should distinguish consumption from what is being dosed to maintain?

Does this make any sense of have I talked myself in a circle?

 

[GainesvilleReef]

The 4th paragraph from the bottom is correct. You can use a reef calculator to back out what you need to add or reduce.

 

[autologyx]

Thanks for the reply. My levels are always very stable. What I add is balanced to the need but I've made the complete transition now from years using Calcium reactors to the DIY AllForReef mix (Carbo Calcium + Bio Mag + A- and K+) and that gave me the opportunity to calculate what I as actually using in terms of Calcium etc.

The question arose because I started to think about how it should be expressed. Depletion in dKH, absent a volume doesn't tell you anything about how much is actually being used I suppose was the point.

I've just dug out an all CarboCalcium container. Interestingly (aside from the discrepancy in what it says about 4,000 degrees KH per 100g on the website and 3,000 on the container...??) when you un-peel the inner label and look at the solution directions it is using litres as the unit of measurement so I think that all squares.... except that I had forgotten that I originally took the decision to halve their formula (preferring to dose twice as much of a weaker solution) which of course throws all the calculations out by the same i.e. 100ml per day is actually the equivalent of 50ml of their recommendation. All other values the same - 0.5dKH per litre added to maintain a 1dKH requirement per 24hrs in that display volume which is around 1g of calcium.

50ml per day checks with what you might expect this profile of display to need given size and stocking based on anecdote I think.

Thanks again.

 

[Randy Holmes-Farley]

Surely without the unit of volume, all that number can tell you is that -for that display, relative dKH drops by 1 degree i.e. showing what the impact of NOT adding any supplemental Calcium Carbonate would have, NOT what you are actually needing to add for a given volume of water to maintain it.

The simple answer to that question is that dKH is a chemical per volume unit of measure already.

1 dKH = 0.36 milliequivalents of alkalinity per liter

 

[autologyx]

The simple answer to that question is that dKH is a chemical per volume unit of measure already.

1 dKH = 0.36 milliequivalents of alkalinity per liter

Right.. well that was the obvious answer I feared..

Perhaps I have got the rest of it wrong too.. when looking at depletion (i.e a measurement over a period absent supplementation) vs calculating consumption it's possible to observe a 1 degree drop for given display volume that can be maintained by a smaller degree-per-litre dose (say 0.5)? Thinking it through now (all measurement units being the same) I think not, yet my actual measurements don't agree.

 

[Randy Holmes-Farley]

Right.. well that was the obvious answer I feared..

Perhaps I have got the rest of it wrong too.. when looking at depletion (i.e a measurement over a period absent supplementation) vs calculating consumption it's possible to observe a 1 degree drop for given display volume that can be maintained by a smaller degree-per-litre dose (say 0.5)? Thinking it through now (all measurement units being the same) I think not, yet my actual measurements don't agree.

If the tank declined by 1 dKH in alkalinity, then a calculated amount of 1 dKH will be needed to bring it back, regardless of the volume.

The calculation, of course, must use the tank volume, to determine how much of a supplement is needed.

 

[autologyx]

Yes that makes sense. I need to revisit this. Either my calculation is wrong, or the consumption observed (absent dosing) is wrong as they should agree yet are out by 50% (I appear to be dosing 50% less at 0.5dKH per litre than should be required (observed drop of c. 1dKH per 24hrs)).

 

[Randy Holmes-Farley]

Yes that makes sense. I need to revisit this. Either my calculation is wrong, or the consumption observed (absent dosing) is wrong as they should agree yet are out by 50% (I appear to be dosing 50% less at 0.5dKH per litre than should be required (observed drop of c. 1dKH per 24hrs)).

Are you using a good estimate of the actual water volume, not the aquarium size?

 

[Randy Holmes-Farley]

less at 0.5dKH per litre

That isn't a thing. It is just "0.5 dKH".

 

[autologyx]

That isn't a thing. It is just "0.5 dKH".

right of course

 

[autologyx]

Are you using a good estimate of the actual water volume, not the aquarium size?

Yes, carefully measured when it was filled.

 

[Randy Holmes-Farley]

Yes, carefully measured when it was filled.

Accounting forrocks and other stuff in it now?

 

[autologyx]

Accounting forrocks and other stuff in it now?

Yes. As always that was with everything in. Its out by no more than +/-5l I'd say allowing for minor adjustment to final chamber in sump over time. I think the error must be on the measurement of depletion side. I've double checked my calculation making sure I allowed for the half strength solution. There is a question over exactly how much dKH the Carbo Calcium provides per 100g given the variation between web site instructions and packaging, but that's out by a factor of .25 (one says 3,000 units, the other 4,000).

The one thing that is at the back of my mind re. Calcium Formate was something that I read about the way the Carbonate is delivered. I can't remember now the precise detail but the context was around why conventional test kits might not read right when using CarboCalcium. I think it was Tropic Marin who published it.. I'll see if I can find it. I wonder if that has any part to play?

Thanks by the way for clearing up the original question. As always with these things they seem very obvious when player back. It just needs someone to confirm it and then the pieces fall into place!

 

[Randy Holmes-Farley]

Oh, you are using carbocalcium?

That product will not show alkalinity in the water unless and until it is metabolized.

 

[autologyx]

Sorry for the delay replying.
Attach files
Yes that was my understanding that the Carbonate is locked up until it can be consumed. I guess in a sense it is offering headroom that might explain the apparent difference between measured drop and what I am dosing? (c. 1dKH drop, but seemingly only requiring 0.5dKH addition to remain stable)?

 

[Randy Holmes-Farley]

Sorry for the delay replying.
Attach files
Yes that was my understanding that the Carbonate is locked up until it can be consumed. I guess in a sense it is offering headroom that might explain the apparent difference between measured drop and what I am dosing? (c. 1dKH drop, but seemingly only requiring 0.5dKH addition to remain stable)?

Sorry, I'm not following really what those words mean. If there is a 1 dKH drop but 0.5 dKH keeps it stable then how is there a 1 dKH drop?

Remember, the drop is depends on the alkalinity. it is far higher in dKH per day at 11 dKH than at 7 dKH. So as alk declines, the daily drop also declines.

If there is substantial formate in the water, it becomes very complicated to tell what the alkalintiy will become in the future since some of it will be metabolized.

 

[autologyx]

Sorry, I'm not following really what those words mean. If there is a 1 dKH drop but 0.5 dKH keeps it stable then how is there a 1 dKH drop?

Remember, the drop is depends on the alkalinity. it is far higher in dKH per day at 11 dKH than at 7 dKH. So as alk declines, the daily drop also declines.

If there is substantial formate in the water, it becomes very complicated to tell what the alkalintiy will become in the future since some of it will be metabolized.

Sorry, I appreciate I'm probably making this harder than it should be! What I meant was that if dosing of the CarboCalcium mix is omitted on that display, I observe a 1dKH drop in a 24hr period. Yet when calculating how much dKH I am adding (calculated with reference to the volume of solution added with reference to the 4,000 dKH per 100g that Tropic Marin suggest it contains), it seems that I am only adding around 0.5 dKH per day.

At risk of complicating and confusing this further.. where formate is concerned, is the measured alkalinity (the GHL unit I have used titration with a PH probe) somehow skewed by this? or is the locked up formate simply potential future alkalinity i.e. in a sense offering a degree of headroom that can be consumed when required?

 

[Randy Holmes-Farley]

I would not take one measurement of the drop to be especially precise since it involves two different alk determination, neither of which is error free.

The drop and the actual value are both complicated when using formate, and for that reason, Tropic Marin suggests going to0 calcium, not by alkalinity.

 

[GlassMunky]

@Randy Holmes-Farley this thread made me think of a question that maybe you can answer.
I have a 75g coral QT tank that is pretty full, and consumes roughly 1dkh per day through me dosing.
when I move all these corals up to the main 220G display (tank receives no dosing now since there’s no corals)
Will the amount of ALK additive need to be adjusted due to the larger volume of water or will the same amount of supplement still add the same amount of carbonates regardless of how much water it’s going into?

does this make sense?
my thought is that if said solution is a set strength, and my corals are consuming the same rate, then I shouldn’t need to change anything since I’m still dosing the same amount of carbonates (am I?)

 

[Randy Holmes-Farley]

@Randy Holmes-Farley this thread made me think of a question that maybe you can answer.
I have a 75g coral QT tank that is pretty full, and consumes roughly 1dkh per day through me dosing.
when I move all these corals up to the main 220G display (tank receives no dosing now since there’s no corals)
Will the amount of ALK additive need to be adjusted due to the larger volume of water or will the same amount of supplement still add the same amount of carbonates regardless of how much water it’s going into?

does this make sense?
my thought is that if said solution is a set strength, and my corals are consuming the same rate, then I shouldn’t need to change anything since I’m still dosing the same amount of carbonates (am I?)

If the corals calcified at the same rate (they may not) and they were all of the demand in the frag tank (meaning nothing else used alk in it), then the amount added as a supplement stays the same, even though when referred to in dKH, it is a smaller value (because it is a larger water volume).