Lab Test Results In - Saltwater Elements - Depletion Over Time / No Dosing

So the results are in! 

I sent a sample off to Fauna Marin to see how the chemistry of my aquarium water was.

This tank had been setup for around 5 years and had NEVER been dosed with anything. Just regular water changes with synthetic sea salt - 5-10% changed every 2 weeks.

Some of the results are surprising! - others as to be expected and even reaffirming already well documented theories.

The tank in question has now been shut down but the reason behind the test was to see how water chemistry and specific elements might be depleted over time when no dosing was carried out. Admittedly there wasn't much in the way of hard coral to take up calcium etc but this tank had house some LPS and SPS over the years.

If you want to view the whole test results from Fauna Marin click here

or a brief overview below:

Reef ICP Results


The  things to note were:


PHOSPHATE HIGH (this was due to letting tank go a little as was concentrating on the new aquarium - would normally be at a lower level)



Some trace elements such as NICKEL / ZINC / MOLYBDENUM missing.

Many of the elements were on the high side but this is to be expected from synthetic salt mix where elevated levels are added.

Perhaps surprising was there was NO depletion of calcium or magnesium.

calcium test reading reef aquarium tank fish

It should be noted however that there is little in the way of hard corals or other calcium hungry inverts in the tank at time of testing - still bit surprised that it wasn't a little depleted though.

The Iodine thing is the real eye opener here, I already knew it was important and read many times that experience aquarists add this element. That has been confirmed and I will now go and buy Iodine test kit and supplements for sure.

I'm not overly concerned with the lack of some of the other elements although I will look into these further. Of course I have no setup and completely new aquarium with new fresh water but it still helps me in that I should expect the new tank to fair much the same over time. I may want to keep SPS and other hard corals so testing will be important going forward. 

Early conclusions to the question

Can a reef tank stay healthy over time without dosing?

Yes and NO.....Iodine at least it seems must be dosed by the aquarist and possibly some other elements, especially when the tank has been running for several years.  I think it shows that calcium and magnesium can be maintained very well though, especially in a softie / anemone tank with water changes alone.

An aquarium packed with hard corals however would certainly use these elements up differently.

So 2 more thins for the shopping list going forward, an IODINE test kit and supplement. I would also like to send off a sample from my new aquarium to see how that compares, and in fact compares to the values given on the bucket!



Phosphate was higher than usual due to tank being disturbed and not maintained quite as well before move - the PO4 reactor had also been taken offline and this was the result.


Not detected - important? an error with the testing process? this element and several others needs more looking into by me.


I would now like to submit a sample from the newly setup tank to compare results - this was worth doing for sure as gives a good incite.

click here to view reef tank diary from the beginning or latest update