Help requested: salinity

[Neoma]

I'm very confused...

I have a one-gallon tank. The lid has a hole for feeding, etc., so water evaporates.

I have been topping it off with RO water per Petshrimp.com:

Add RO or distilled water whenever the level of your tank drops by more than about 10%. You do not need to add any more salt because the salt stays in the tank, and the evaporation causes the remaining water to be saltier. How often you need to replace water will depend on the size and shape of your tank.

Today, I was having a conversation with someone on another opae ula forum that lead me to believe that the salinity will become diluted over time if I just keep adding RO water.

I really don't want to mess with changing the salinity. Per Mustafa's instructions, I have never checked my salinity since I mixed the water with the prescribed amount of salt at the onset.

I would love to hear from more experienced opae ula keepers than myself.

I set this tank up in March or April of last year. The shrimp seem to be doing fine, though I have never had a berried female. (I don't know if that's a measure of tank health, but I thought I'd throw that in there.)

[dglidden]

Salt doesn't evaporate. As the water evaporates, the salt in the water remains the same amount, which increases the percentage of salt to water, i.e. the salinity goes up a little. When you add more RO water, there is no salt in it, which will then reduce the percentage of salt to water, i.e. the salinity goes down a little. As long as you're topping-off and not over flooding or letting it evaporate a whole lot, you're maintaining roughly the same salinity.

If you're keeping the same amount of RO in the tank, the salinity will remain the same. Not sure what that other person is talking about.

[Neoma]

Salt doesn't evaporate. As the water evaporates, the salt in the water remains the same amount, which increases the percentage of salt to water, i.e. the salinity goes up a little. When you add more RO water, there is no salt in it, which will then reduce the percentage of salt to water, i.e. the salinity goes down a little. As long as you're topping-off and not over flooding or letting it evaporate a whole lot, you're maintaining roughly the same salinity.

If you're keeping the same amount of RO in the tank, the salinity will remain the same. Not sure what that other person is talking about.

Thank you, dglidden! That's very clear! I appreciate your help.

[Vorteil]

Also the shrimp are used to a wide range in fluctuations. Salinity changes won't affect the shrimp.

[Neoma]

Also the shrimp are used to a wide range in fluctuations. Salinity changes won't affect the shrimp.

Thank you, Vorteil. That's very helpful.

Yes, I forget that, in the wild, their water conditions change regularly.