Thanks for the feedback, its hard to believe that a trace element such as potassium (for which I have never dosed prior) in my reef tank that has been running for almost 20 years and only do once a month to once every two month 10% water changes can have a level of 273 which I can only assume was likely the level for the past several years with no dosing only increased to 313 after adding a quantity that should have brought to 400. I would have thought the depletion must be pretty slow if it was 273 with no dosing. Hard to believe it went up to 400 and then back down to 313 in a few months.
I understand the frustration, I went through the same.
Addition of an element to appropriate levels does not mean this will result in proportionate consumption. So when you had for 20 years 273, then raise it to 400, it will not mean it takes 20 years to get it back to 273.
For K / Potassium, I never had to dose it until I started using Zeolite. Now I have to regularly dose it.
In (over) simplified terms, this is due to the bacterial consumption which will take up additional potassium until saturated, but will then be flushed out through skimming.
From your ICP report, I can see that you are most likely not using Zeolite, but your biofilm might still consume this once exposed to higher levels.
In a state of deficiency, this process is impaired and will then bottom out at a certain level, which is not desirable, i.e., in your case low potassium levels, and others.
Same for iodine and some others that seemed to drop back almost to prior levels. Then there are other elements that I dosed, such as vanadium, to bring to recommended level, and they are back at zero. I can rationalize that maybe these were immediately consumed upon dosing if there was a latent demand for the element by organisms.
I would broadly agree with this. Added elements, will be consumed as much as possible, back to previous low levels if limited to one time dosing.
So what I thought was an easy exercise of calculating initial dose then expecting it to reach calculated levels then testing a few months later to determine regular depletion for a maintenance dose doesn't seem that straightforward.
It is not straightforward, as it is different for every tank as it is based on your tanks biofilm profile and other export measures.
With depletion seemingly largely inconsistent how do I come up with maintenance dosing quantities.
Some do not need to be shown on the ICP as long as there is sufficient import you provide on a regular basis, e.g., thorough 1-part/2-part/3-part/X-part dosing.
The pdfs normally have recommendations which show which are these, so you can focus on the ones that matter, but yours is only the small/inexpensive ICP which does not have this information, including not showing salinity, nitrate, and orthophosphate (and some others I cannot remember). This particular limited test should only be done if doing ICPs more frequently - the more comprehensive test is the Reef ICP Total.
Also, the ones that matter are a heavily disputed topic, but the pdfs provide ‘a’ way of approaching this in the Reef ICP Total test only.
I'm not interested in doing monthly ICP from a cost perspective and seems I have a high risk of overdose if I try to use just a few data points to calculate a maintenance dose.
Unfortunately, you will not get this resolved properly with only a couple of ICPs.
The risk of overdose is not necessarily high, but you should also not dose if you do not have to.
What could be a safeguard is that you limit regular dosing, in addition to one time adjustments,
to what was consumed between the the last two ICPs you have available.
Meaning that you take the adjustment dose, add it to the tank, and then continue dosing over the next three months (the time between the two ICPs) this same adjustment amount for the elements which have shown to be lower in the most recent ICP even though you adjusted them after your initial ICP.
This should get you closer to target amounts (roughly), without frequent ICPs, but some amounts might still shown to be lower.
Without knowing the salinity this was measured with, it looks like you actually have only a few parameters which are concerningly low, in my opinion.
Potassium
Strontium
Iodine
Vanadium
Molybdenum
From these, I would recommend to definitely try to increase all but Strontium, although I also believe Strontium should be increased, but the value of dosing Strontium might not be as agreeable.
I also think Zinc should be a bit higher.
The reports are from Fauna's website I just provided the version that was most compact. Attached are PDF versions.
Apologies, you are downloaded the ZIMS file version of this, which I never did, and it looked strange.
