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Re: conductivity question

On Wed, 20 Jan 1999, Roxanne Bittman wrote:

> I recently measured the conductivity in my 40g
> aquarium, and was suprised to see it measured
> 660mS!!

I assume that with mS you mean microSiemens/cm, not milliSiemens/cm.  If I
remember right, my tanks read around 600-700 -- higher than the tap water
because of evaporation and feeding, mostly.  That's "fresh" water but it
might be higher than you have in mind.

> I am curious to hear what other curious aquarists
> measure in their own tanks.  I use R/O water (which
> measures 0), but I add the following with every water
> change:
> 1/2 tsp. Kents R/O Right
> 1 calcium carb. pill, every third time
> 1/2 tsp. MgSO4, every third time
> 1/2 tsp. KNO3
> 1/2 tsp. KSO4
> However, and this is a big "however", I have had this
> darned "green water" aka floating BG algae problem
> lately, and have been treating it by adding additional
> KNO3, after testing for nitrate (which consistently
> reads zero).  I added additional 1/2 tsps every day last
> week.  I measured after this.

Any electrolyte that you add to the tank will increase the conductivity.
In proportion to the amount you add.  The exact proportion varies from
chemical to chemical.  All of the chemicals you listed above are

> Question is, is 660mS bad (for plants?) (for neons?),
> etc.

Probably high if you want to breed neons but I think they'll live in it
just fine.  Plants do show distinct preferences for water of different
salinities, but I think those preferences show up more as you get toward
higher conductivities -- like 5000 microSiemens/cm and up.  I've seen
plants (admittedly, not a large variety of plants) growing in and around
saline springs with a conductivity over 60,000 microSiemens/cm -- more
saline than sea water, which is about 35,000 microSiemens/cm.  The same
(?) plants also flourished in water with 12,000 microSiemens/cm and a very
clean sand substrate.

> A friend's less heavily managed tank measured
> 56mS, as a comparison.  The "springs" in The
> Optimum Aquarium measure in this range as well.

That's very low.  From what Dr. Dave has said I'm a little surprised that
water with a conductivity that low would contain enough Ca++, Mg++, K+ to
support good plant growth.

Roger Miller