How important is strontium [Archive] - Reef Central Online Community

Randy Holmes-Farley

01/16/2010, 11:05 AM

I do not consider it important at all. I do not measure or supplement it, and I generally doo not recommend others do so either.

There is no good evidence that it is needed by the organisms we keep.

I discuss it here:

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 2: What Chemicals Must be Supplemented
http://reefkeeping.com/issues/2007-04/rhf/index.php

Strontium and the Reef Aquarium
http://www.advancedaquarist.com/issues/nov2003/chem.htm

Magnesium and Strontium in Limewater
http://www.advancedaquarist.com/issues/dec2003/chem.htm

from the first one:

http://reefkeeping.com/issues/2007-04/rhf/index.php#18

Supplementing Strontium
Strontium may or may not be useful in coral reef aquaria, and it may or may not become depleted. Like magnesium, strontium becomes incorporated into calcium carbonate in place of a portion of the calcium ions. That incorporation happens to approximately the same extent whether a coral skeleton is being formed, or an abiotic (nonbiological) precipitate on a pump’s impeller. It is just a fact of life that strontium looks a lot like calcium, so it gets into places where calcium would otherwise be. Some aquarists have concluded that strontium may help corals to deposit their skeletons despite the absence of any evidence of this in the scientific literature, and of any direct experimental evidence (for or against) by hobbyists.

Some hobbyists do report positive effects of dosing strontium. Scientific evidence indicates that some organisms need strontium, albeit not the organisms that most reefkeepers maintain. Certain gastropods, cephalopods and radiolaria, for example, require strontium. There is, however, no clear evidence of any benefit of supplemental strontium in coral reef aquaria.

A few years back, when I tested my aquarium’s water for strontium (using a sophisticated lab machine), I found that in my reef aquarium, with no recent strontium additions, strontium was already elevated (15 ppm) above natural levels (8 ppm). By testing the Instant Ocean salt mix that I was using, I found that it, too, was elevated (15 ppm). I saw no evidence of depletion, at least not when performing my routine of changing 1% of the tank's water daily. I would not like to see the strontium level get any higher, because strontium is known to be toxic to some marine organisms at levels not too far above that. Consequently, adding a supplement without knowing the aquarium's current strontium level is not advisable.

Overall, water changes with a salt mix containing a suitable level of strontium may be the best way to keep strontium at appropriate levels, assuming it has any benefit at all. That requires no testing or worrying about dosages. For those who want to dose strontium, or who have very high calcification rates, which may deplete strontium faster than it can be replaced by water changes, I recommend testing to ensure that it does not get too high. My recommendation is to maintain strontium levels in reef aquaria in the range of 5-15 ppm. That level roughly spans the level in natural seawater of 8 ppm. I do not recommend that aquarists supplement strontium unless they have