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Yesterday, I added 1/4 cup of non-iodized salt to my 5 gal planted tank, currently not in use (no fish). I calculated a final NaCl concentration of 0.41% or 4.1 ppt. (Seawater is 3.5%.)

The salt should kill Ich and a whole lot of parasites, but what will happen to the plants??

Explanation: Scientific literature has confused me mightily on this subject. Observational studies show that aquatic plants don't live in habitats with 0.1% salt, but that's long-term exposure for years and years. One experimental study* that I'm working from now shows that 0.29% salt did not inhibit growth of Salvinia natans, a salt-sensitive species. The morphology of plant changed dramatically over the 2 week test period, but not the growth rate. A doubled salt concentration of 0.58% inhibited growth a fair amount, but it didn't kill the plant.

The investigators said that the cause of the salt injury was that Na+ blocked K+ (potassium) uptake, which prompted a severe K+ deficiency. That sounds reasonable to me, since these two similar ions often compete. They also suggested that larger plant species would be more salt-tolerant.

SO fellow-APCers... The burning questions I have are: Will my plants survive 5-7 days of 0.4% saltwater? This is a fairly high salt concentration; it may be more than necessary for fish diseases, since 0.1% salt apparently kills Ich parasite.

If the plants die, I can try again with a lower salt concentration and perhaps try adding K+ to the water. Oh, this is fun!

Pictures show 5 gal tank before adding the salt and then immediately afterwards. Notice that the salt turned the water a little cloudy.

*Jampeetong A and Brix H. 2009b. Effects of NaCl salinity on growth, morphology, photosynthesis and proline accumulation of Salvinia natans. Aquatic Botany 91: 181-186. (I was able to download entire paper off the Internet via Google Scholar.)
 

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This is very interesting!

If plants can survive for a shorter period of time, this possibly really opens up new ways to threat parasites in a planted tank!

So far when I had an issue, I have always removed all fish from the tank to a bare bottom tank an treated the fish there and hoped that the stuff dies out in the planted tank with no host.
BUT this is a lot of hassle. Just alone removing quick swimming fish from a large planted tank can take hours for me.
(Not that I have many problems with parasites. For me the best way is just not add new fish to the tank as long as I can avoid. I found fish and shrimp live long in my NPTs.)

Silly question: I guess removing the salt is as easy as doing water change? It does not bind to stuff or accumulates in plants?
 

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Hello Diana,

I am happy to read other researches in the hobby. In hungary, often there is a problem with the tap water with too much salts. We measure the KH and the GH, if the KH more, than GH, the water is probably not good for plants. I think it is because of the Na ion, and the high alkalinity. The high KH because of the high NaHCO3 and NaCO3 concentration. The simplest way to fix it to raise GH with CaCL2 and MgSO4 in good ratio, and maybe mix the tapwater with deionized or RO-filtered water.
The extra Ca and Mg ion partially disposes the Na ion. The Na ion make antagonism with 3 other ions: K, Ca, Mg, according to the scientific literature.

This experiment could show wether the high KH water is bad not only because of the Na, but the high HCO3 content, that obstructs the plants fairly ( lower CO2 in the water, rather HCO3 and CO3, these carbon sources are harder uptakeable for plant) And I read that high HCO3 concentration make ion antagonism between some other nutrients.
 

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Discussion Starter · #5 ·
I guess removing the salt is as easy as doing water change? It does not bind to stuff or accumulates in plants?
Water changes would remove the salt from the water in a logical manner, because it would not form precipitates. A 50% water change should cut the water's salt concentration in half.

In theory, Na might displace some K on soil particles. Plants would definitely accumulate more Na in their tissues. However, once the salt is gone, it should dissipate gradually and without problems from the ecosystem. New plant leaves will develop with less Na in their tissues.
 

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Discussion Starter · #6 · (Edited)
....The Na ion makes antagonism with 3 other ions: K, Ca, Mg, according to the scientific literature.
Thanks very much for your input, which stimulated another "look-see." I went back to the Jampeetong's paper. At 0.29% salt*, the plants showed a HUGE (~60-70%) decrease in tissue K. Higher salt concentrations further reduced K dramatically in both roots and leaves.

Ca and Mg were less affected. For example, tissue Ca was reduced about 25% in leaves and none in roots. A doubling of the salt concentrations to 0.58% had no further effect.

For Mg, salt had no significant effect on roots, but 0.29% salt did reduce the leaf-Mg by about 50%. A doubling of salt concentrations to 0.58% brought the leaf-Mg down slightly.

Bottom Line: K is the main nutrient that competes with Na. Mg to a lesser degree.

I suspect that plants will tolerate a salt addition much better in the presence of adequate K. Therefore, I predict that hobbyists with softwater (not much K of Mg) would probably see more problems with salt treatment than those like myself with hardwater. A simple solution would be to use marine salt mixes (e.g., "Instant Ocean") instead of ordinary salt. Solar salts also would work. These salts would automatically provide extra K, Mg, Ca, etc without decreasing the overall osmotic killing capacity towards parasites and bacteria. Indeed, Dr. Noga (Fish Diseases, 2000, p. 295) recommends using them for saltwater treatments.

*Quantitative Stuff: Jampeetong expressed values throughout his papers as mM. For example, his 50 mM NaCl is equivalent to 0.29%, the value that I'm using here.
 

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Thanks very much for your input, which stimulated another "look-see." I went back to the Jampeetong's paper. At 0.29% salt*, the plants showed a HUGE (~60-70%) decrease in tissue K. Higher salt concentrations further reduced K dramatically in both roots and leaves.

Ca and Mg were less affected. For example, tissue Ca was reduced about 25% in leaves and none in roots. A doubling of the salt concentrations to 0.58% had no further effect.

For Mg, salt had no significant effect on roots, but 0.29% salt did reduce the leaf-Mg by about 50%. A doubling of salt concentrations to 0.58% brought the leaf-Mg down slightly.

Bottom Line: K is the main nutrient that competes with Na. Mg to a lesser degree.

I suspect that plants will tolerate a salt addition much better in the presence of adequate K. Therefore, I predict that hobbyists with softwater (not much K of Mg) would probably see more problems with salt treatment than those like myself with hardwater.

*Quantitative Stuff: Jampeetong expressed values throughout his papers as mM. For example, his 50 mM NaCl is equivalent to 0.29%, the value that I'm using here.
Jampeetong and you used simple NaCl? Could you repeat the research with NaHCO3, with same Na concentration?
 

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Discussion Starter · #8 ·
Jampeetong and you used simple NaCl? Could you repeat the research with NaHCO3, with same Na concentration?
Yes, I used simple NaCl. I'll let you do the research with NaHCO3. That involves plant carbon uptake, which is an entirely separate issue from my purpose.
 

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Discussion Starter · #9 ·
Three Day Update: I took these photos this morning, 3 days after I added the salt. The plants seem to be doing okay, except for the Vallisneria spiralis. It seems to be melting a bit. pH is normal.

You'll note there's a fish in the tank. Two days ago, he was in my 20 gal "holding tank" with about 10 other precious guppies. He had something on him--two white pimples and a discolored patch that looked very suspicious. So, I threw him into the experimental tank. Very convenient! This morning, the pimples and discoloration on his fins are gone.

Tentative Plan: I'll wind up this experiment in 7 days with water changes. At that time, I may add some KCl (salt substitute from grocery store). If the fish continues to look good, I'll probably return the him back to his home on Day 5. By then, he will have had 4 days of 0.41% salt treatment.
 

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Bottom Line: K is the main nutrient that competes with Na. Mg to a lesser degree.

I suspect that plants will tolerate a salt addition much better in the presence of adequate K...
Little side note: I used to go on long kayak trips, sometimes paddling 12-16 hrs a day. "Water snacks" are usually crackers, trail mix, jerky, preserved foods with very high Sodium. One year I did a trip with a paddler who was a nutritionist. He taught me to follow up these salty snacks with a banana because the high Sodium diet isn't as bad if we offset it with high Potassium. After adopting that strategy I just felt better at the end of trips, less heartburn, less cramping, etc. and I was thankful for that knowledge. Fortunately, I'm not one of the superstitious folks who believes a banana on your boat brings bad luck! I've felt the benefits of K easing the downsides of Na, just never really thought about it for my aquarium... So cool!
 

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Discussion Starter · #13 · (Edited)
Sorry folks, but it looks like this pilot study didn't yield much useful information. In general, I would not add salt to planted tanks to treat fish diseases. (For salt treatment, I would use separate hospital tanks or salt baths.)

Plant Sensitivity: At 3 days (5/11), I did a 75% water change to reduce salinity from 4 ppt (0.4%) to 1 ppt. I could see that the plants were affected and I didn't want to lose them. Hygrophila difformis leaves were starting to detach from the stems. Vallisneria spiralis leaves starting to look injured. Frogbit turned brown. Water Soldier and small duckweed seemed okay. After the water change, I also added 1/4 tsp of "salt substitute" (KCl) to water.

Four days later (5/15), I did a 50% water change to reduce salinity from 1 ppt to 0.5 ppt. Plants are recovering, so it wasn't a wipe-out. The tank is now back to raising baby guppies.

Salt treatment for fish diseases: The salt levels used for prophylactic treatment of fish is 1-5 ppt according to Dr. Noga (Fish Diseases, 2010, pp. 414-415). For treating ich, he cites successful treatment with 5 ppt.

The odds of finding a salt concentration that will kill parasites but not plants looks increasingly elusive. :doubt:
 
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