Taken from "It's In The Water", by Ron Shimek
http://reefkeeping.com/issues/2002-0...ture/index.php

[Aquarists have] the feeling that organisms somehow "use up," "change," or "consume" many of these [trace] chemicals, and in doing so, forever remove the chemicals from the reef aquarium system. This assumption is not completely false, some chemicals are "used up" and removed from the system, but most are not. Organisms are dynamic entities, and while some chemicals are temporarily sequestered away, such chemicals generally remain available in the system due to metabolic turnover. The only real exceptions to this as far as organisms are concerned are those chemicals, such as calcium, which get incorporated into an insoluble matrix.

Several trace elements are found in elevated concentrations in aquarium water [Table 2; Figure 2]. Some of these metals have extremely high concentrations relative to NSW; tin has already been mentioned as having concentrations over 200,000 times above normal, but Thallium, Titanium, Aluminum, Zinc, Cobalt, Antimony, and Copper all have concentrations of over 95 times normal.

Several of the trace metals varied in concert, particularly Cobalt, Tin, Zinc, Titanium, Copper and Vanadium, and lower but still positive correlations with Nickel and Aluminum are found. All of these metals are found at concentrations far above those of natural sea water. Some of these concentrations are almost unbelievably high. Tin has an average concentration in our systems of over 200,000 times greater than in natural sea water.

Increases in many of these same metals are correlated with the age of the tank. One explanation for that pattern would be that they may build up with the passage of time.

The older tanks also have more ammonia, nitrate/nitrite, phosphorus, iodine and copper than younger tanks.

Many of the trace element concentrations are lower than they are in freshly made up artificial sea water. Whether this indicates organism use, or abiotic chemical reactions, is unclear. Even though these levels are lower than in "fresh" artificial sea water, they are still very much higher than in natural sea water, and may still indicate a cause for concern.

[scrubbers remove metals; skimmers do not]