Getting trace elements uptake/depletion

[potatocouch]

This seems to be the most commonly accepted method to understand reef tank trace elements uptake/depletion:

"Once you have your baseline parameters you will need to know how much your corals consume in a week. The easiest way to figure this out is to wait one week after you perfect your levels and take another test. Subtract the new test from the baseline test and there you have it! If you want a daily average just divide the difference by seven. You can now set your dosing schedule or pump to the proper amounts. It is a good idea to retest your consumption levels every few months as the corals grow. A larger colony will consume more than it did when it was a tiny frag and as you buy corals the consumption increases as well."

So what the above are saying is pretty much set your trace elements to the most optimum levels and ignore it for a week then test again before weekly WC.

Whilst I understand the concept, wouldn't the corals suffer in this 1 week period?

Then once we understand the uptake rates, we don't want to fill the gap in a swift manner as this will shock them hence it needs to be donr slowly at gradual increase?

 

[Randy Holmes-Farley Verified Community Expert]

So let's first clarify. The above quote is almost certainly talking about calcium, alkalinity, or magnesium, but not trace elements, which be definition are present at very low levels and include such things as iron, copper, vanadium, manganese, etc. So it wouldn't be the way to monitor trace elements, IMO.

Second, the above method is useful for a very rough estimate, but it is not perfect because the demand for calcium and alkalinity depends on the starting level of alk. So if you start at 11 dKH and drop to 6 dKH, it might drop 2 dKH the first day and only 0.2 dKH the last day of the week.

Personally, I strongly prefer to select a guesstimate starting dose based on what is in the tank, and adjust it by trial and error over a week or two to stabilize alkalinity (using equal parts dosing of both calcium and alkalinity, assuming you are using a two part system). Adjust the doses every 1-2 days if it seems necessary based on alk measurement. After a week or two, consider adjusting the calcium independently if it seems to be rising too much or falling too much, but recognize that most calcium changes you see are probably just testing noise if the time frame is too short.

 

[potatocouch]

So let's first clarify. The above quote is almost certainly talking about calcium, alkalinity, or magnesium, but not trace elements, which be definition are present at very low levels and include such things as iron, copper, vanadium, manganese, etc. So it wouldn't be the way to monitor trace elements, IMO.

Second, the above method is useful for a very rough estimate, but it is not perfect because the demand for calcium and alkalinity depends on the starting level of alk. So if you start at 11 dKH and drop to 6 dKH, it might drop 2 dKH the first day and only 0.2 dKH the last day of the week.

Personally, I strongly prefer to select a guesstimate starting dose based on what is in the tank, and adjust it by trial and error over a week or two to stabilize alkalinity (using equal parts dosing of both calcium and alkalinity, assuming you are using a two part system). Adjust the doses every 1-2 days if it seems necessary based on alk measurement. After a week or two, consider adjusting the calcium independently if it seems to be rising too much or falling too much, but recognize that most calcium changes you see are probably just testing noise if the time frame is too short.

Thanks @Randy Holmes-Farley

Let's take your example Alk down from 11 dKH to 6 dKH over 5 days period, which the Alk consumption may not be constant 1 dKH per day. The 1st day it may consume 2 dKH and the 2nd day it may consume another 2 dKH then the following days a smaller rate that makes up to 6 dKH total usage for 5 days. [Example #1]

Or it can probably has lower rate of consumption in the first few days then higher rate in the last day. So if I understand from your statement is that Alk (or Ca or Mg) consumption can't be taken as a constant value. It's randomized and can't be predicted.

And obviously we don't want to have significant Alk swing. So from the example #1 above and if using the quoted method, I would be dosing 1 dKH per day and in fact I should've been dosing 2 and then the next day consumption is still high at 2 dKH but am dosing 1 dKH then I'm already behind by 2 dKH. What is the acceptable Alk swing in mixed reef tank (SPS, LPS, softies and zoanthids)?

So in regards to your preference of dosing methodology, your suggestion is to do initial guesstimate on what to dose and adjust it by trial error every 1 or 2 days, over a week or two period. But wouldn't we be in the same boat if we are to use example #1 above?

If I can summarize what my confusion is:

• Alk (Ca & Mg) depletion rate isn't a constant value. It's a randomized value which one can't predict.

• Dosing pump setup requires a constant value even it has the capability to dose higher on day 1 and day 2 and less on day 3, 4 & 5, this wouldn't address the accurate depletion rate (it maybe for that week but for some odd week, it may consume 3 dKH as the coral grows).

So with dosing pump, would it fair to say, no matter how accurate one think one're dosing, Alk swing will still happen? Or have I confused myself?

 

[Randy Holmes-Farley Verified Community Expert]

Well, I wouldn't say the demand is random. We can often look at a tank and estimate the demand, and I do that it my dosing recommendations for my DIY two part. What I meant was that demand is higher for any tank at 11 dKH than at 6 dKH.

http://reefkeeping.com/issues/2006-02/rhf/index.php

from it:

Dosing Instructions

The dosing instructions are basically the same for each recipe, although any given aquarium will end up using about twice as much of recipe #2 as recipe #1 to add the same amount of calcium and alkalinity.

To initiate dosing, first adjust calcium and alkalinity to roughly their correct ranges. This may require a substantial dose of just the calcium part if calcium is low (e.g., below 380 ppm). I would suggest targeting calcium between 380 and 450 ppm, and alkalinity between 2.5 and 4 meq/L (7-11 dKH; 125-200 ppm calcium carbonate equivalents).

This calculator shows how much of what parts to add in order to boost one or both of the parameters by a certain amount:
Reef chemicals calculator
http://home.comcast.net/~jdieck1/chem_calc3.html

Then, once things seem roughly correct, select a starting daily dose for routine dosing. Here are some suggested starting doses, but the exact values do not matter much. The suggested doses apply to both recipes.

After a few days of dosing, note whether alkalinity is low, high or on target. Only bother to test alkalinity, not calcium, during this period, because it is much more sensitive than calcium to over- or underdosing. Adjust the dose up or down as necessary to increase or decrease the alkalinity.

Once you have determined the proper dose, continue it until there is a substantial reason to adjust it (such as falling alkalinity as the corals increase in size). When adjusting the dose, raise or lower both of the recipe's parts together.

Resist the temptation to keep jiggering calcium and alkalinity independently. They will need occasional corrections, but that should not be the normal course of dosing unless there are substantial outside influences, such as water changes with a salt mix that does not match the tank's parameters or an error in making the mixes.

Check alkalinity fairly frequently to make sure the dosing continues at a suitable rate. Check it maybe once a week to once a month (or less as you get more experienced with the system and the tank). Check calcium once a month to once every few months to make sure it continues on track.

Remember to add an appropriate amount of Part 3 each time you finish adding a gallon of Parts 1 and 2.

Table 1. Suggested starting daily doses of this supplement in different aquaria.
Tank Description:.........................Suggested Starting Doses
...................................................Recipe #1:.................Recipe #2
Fish-only with live rock:.................0.1 mL/gallon:.................0.2 mL/gallon
New tank, few corals:.................0.2 mL/gallon:.................0.4 mL/gallon
Low demand:............................0.3 mL/gallon:.................0.6 mL/gallon
Mixed tank:................................0.5 mL/gallon:.................1 mL/gallon
Heavy demand (SPS corals):...........1 mL/gallon:.................2 mL/gallon

 

[potatocouch]

thanks @Randy Holmes-Farley ! much appreciated.

So do "start dose" daily then after few days, test Alk only and adjust the dose according to Alk level.

So concentrate on understanding the Alkalinity first then once understood, do the same to Calcium.

I hope I got it right.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, that's my suggestion.

The other method works too, but only to get the starting dose that you have to then tweak anyway.