Re: Reconstituting RO water with sea salt

Mark Thompson (APL post from September, 1995) suggested reconstituting RO with 1 tsp good synthetic sea salt per 10 gal of water. In his hands, and mine, this gives a GH of about 2, which is satisfactory for my soft water tanks. I also add 1/2 tsp per 10 gal sodium bicarbonate (baking soda), which, with a tiny KH from the sea salt, gives a final KH of about 4.5. I have not looked up the composition of sea salt, but it clearly has some Ca, Mg (measurable KH), potassium, and very likely, other trace elements, in addition to its principal ingredient, sodium chloride. Sodium chloride is not generally believed to be good for plant tanks, but I have seen no evidence that this dose of NaCl has a detrimental effect on my plants (swords, water sprite, hygrophilla deformis, valisneria, crytocorne walkeri and balansae, Anubias nana, rotala macrandra and indica) or fish (angelfish, cardinal tetras, Otos and SIA's). I should add that I am supplementing with Kent freshwater supplements fo!
 r plants, which claims to provide iron, magnesium, manganese, molybdenum, potassium, boron, and other trace elements, at a dose which maintains the iron concentration at about .1 ppm. Also, I emphasize that my tanks were set up relatively recently (three months), so I cannot comment on long-term success. So far, though, I have had to harvest the fast growing plants weekly to prevent their filling up the tanks. Although it is possible that additional trace element deficiencies might crop up with this regimen, I rather doubt it, since fish food clearly contains additional trace elements.

FYI: Tanks: 75, 29 and 10 gal. Substrate: terralit under standard fine aquarium gravel; CO2 (yeast); about 3 watts/gallon wide-spectrum fluorescent. Nitrates, <5 ppm; phosphates, <.1 in the 75, about .1-.2 in the 29,which is overloaded with two breeder angels and 26 3/4 inch babies); iron maintained about .1 ppm.

Unless someone can report evidence of problems with the use of synthetic sea salt plus bicarbonate to reconstitute RO water, it seems that this is a very practical and cheap alternative, at least for soft water tanks. Obviously, generating harder water would require more sea salt to the point that the sodium chloride might well be a problem.

Incidently, it has been frequently reported on the APL that the commercial pH adjusters which claim   to provide KH are merely baking soda. (Sodium hydrogen carbonate = sodium bicarbonate = baking soda). Doubtless much cheaper from the grocery store.

Rick Denney
rdenney at ibm_net