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[APD] Water and "electrolytes"

An exchange on APD, earlier, with Bob Dixon, made me realize that we spend lots of words on hardness, pH, osmosis and tds, but we rarely discuss the cellular function of electrolytes. I'd love to learn more about them and their operation.

Medical types usually define blood electrolytes as Ca++, Mg++, Na+, and K+. The first two are divalent ions that contribute to hardness and the others are monovalent and not involved in GH at all (i.e., don't make soap scum form). All are important to transporting "stuff" across cell walls. I think their ratios are often more important than absolute quantity.

I had seen several fish stores killing Discus by trying to keep them in pure RO water, which surprised me, but the problems really came home to me when I moved to Modesto, which had ridiculously soft water after my lush and healthy 300 ppm (200 ppm hardness) water in Fremont.

At 50 ppm it had 0 degrees of both General and Carbonate hardness. The main ions were from silicates and (maybe) aluminum. I killed much of my Java Moss and nearly killed some nice killifish before I caught on. "Dead Soft" indeed!

With such low tds, I reasoned a bit of salt would reduce the osmotic pressure across the cell barriers and hence reduce strain on fish and plants.

Wrong! My Java Moss, which is a salt-loving estuarine plant in many places, bit the dust (well, it melted and turned brown), fast. Jave Fern (another salt-tolerant plant) was also in obvious distress. The fish didn't say much, but they, too were obviously not very happy.

I added a bit of Seachem's "Equilibrium" and got a turnaround so rapid that the plants looked better the very next day! Somewhere I had remembered a bit of trivia that divalent and monvalent ions were essential to many cell transport processes, and that bit of trivia saved the day.

Within weeks, I had lush plant growth in all my tanks, and the fish were happy and breeding well, again.

Two lessons I learned from this:

1) Salt, sodium chloride, can be deadly if there is no Ca or Mg to go with it to balance the electrolytes, and

2) Low tds water isn't the "to-die-for" water that some fishkeepers yearn for. I have done best with true rainforest fishes at 80-120 ppm tds, with about 2/3 of that from Ca/Mg hardness. Most plants love it if the electrolytes are even roughly in balance.

Barry Cooper went through a similar process when he moved from Cornell NY to OR. We corresponded on it and I'm not sure what parts were whose ideas. As a veterinary pathologist, I suspect he made the larger contribution, but I rely on my aging memory to avoid giving him too much credit. :-) We were busy discovering much the same things at about the same time.


Wright Huntley - Rt. 001 Box K36, Bishop CA 93514 - whuntley at verizon_net
                    760 872-3995

Eschew obfuscation and bloviation!

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