truly ideal alk / Ca2+

[aujay]

I have read several different places (websites, test kits, threads, etc.) different goals for calcium and alkalinity. I was wondering what the true ideal was... And why its not the same as natural sea water...

[KDodds]

Well, it depends on who you ask, hence your differing responses. If at all possible, I prefer to keep things as close to NSW as I can. Following that reasoning, my Alk is a little low, compared to what others will tell you is "ideal", at 2.7-2.9meq/L. My Ca sits over 450. Both are steady, along with pH which varies by 0.04, maximum, within the 8.2 range, which is really more important (within reason, of course). This is accomplished through the use of a Nilsen and Ca Reactor in conjunction with a pH controller. It is, IMO, one of the best things I've ever done, eliminating the need for daily dosing, and keeping the system more stable than any other water quality maintenance scheme I've encountered besides constant replacement with NSW as is done in some public aquaria.

[Highlander]

I always go by the target zone in this article:

http://www.advancedaquarist.com/issues/nov2002/chem.htm

[KDodds]

Oops, forgot to mention that a lot of people keep their Alk and Ca higher than NSW levels to compensate for lack of maintaining them. IOW, keeping Alk at 4meq/L allows for more room to "drop" and still be within NSW range. Same holds true for Ca with the exception that many organisms seem to do better with higher Ca levels than those found in NSW. Possibly this would be due to increased availability in proximity to these organisms, since they're all sessile (Clams, Corals, Coralline Algae).

[Randy Holmes-Farley]

An number of factors may make levels other than "natural" be more appropriate for a reef aquarium, not the least of which are:

1. Aquarists may want the corals to grow faster.

2. Tanks have factors that the ocean does not have that stress them, and make keeping higher alkalinity or calcium levels desirable, such as low pH, low natural foods, and high phosphate, organics, or nitrate.

3. With nonconstant dosing, levels will drop between doses, so they may need to be much higher than NSW to prevent them from dropping below NSW before the next dose. This is especially true for alkalinity.