Some saltwater questions

[Mosaic]

I've been thinking about a few things.

1. When I make RO/DI water I always save some in gallon jugs for top offs. Can I store saltwater I mix up too? Would it be okay in the jug for a week, or will it degrade in some way?

2. Is there some sort of formula to figure out how much I need to top off? Like SG / tank volume = amount of FW to add. I've got a pretty good feel for it by now, but I was just curious.

3. A higher SG is recommended for reef tanks. Is this because they need the higher salt levels, or is it because with more salt comes more of the other minerals in salt mix that they need? Or some other reason?

 

[roka64]

1. You can store it for a week, if you seal it, otherwise use a ph to to keep the water moving. Personally, I start to premix my SW on friday, add salt, heater, ph and let it stew until Sunday and then do my PWC.
2. I just set up the tank, full of SW and what evaporates, I replace with FW for top off.
3. I believe they require higher salt levels (but we will have to wait for a more knowledgeable person to explain further). I keep my FOWLR at 1.020ish and my new 125 will stay at 1.024 because I am planning on some corals.

 

[tecwzrd]

1: Keep it as long as you want but make sure ph/sg/temp is still the same as the main and if you don't have ph running the whole time at least mix it up for a couple of hours before you use it to oxygenate it again.

2: I top off daily to keep the sg from changing too drastically. If you haven't been able to top off daily (gone for the weekend for example) then top off half the usual and the other half a couple of hours later. There is no set formula since tanks evaporate at different levels due to the environment, lights, temperature, ect....

3: Higher for reef tanks because it's closer to natural ocean salinity levels. With a higher sg heat/sg/ph changes can be more dangerous and need to be adjusted/monitored more closely.

Reason for keeping it lower is less salt use, less stress on new fish/mobile inverts to acclimate, and leaves a little more room for error i.e. heat fluctuations, sg rising/falling too quickly from evaporation, ph fluctuations. ect...

 

[MT79]

or is it because with more salt comes more of the other minerals in salt mix that they need?

Bingo. It helps provide the right Alk/CA, magnesium levels, among others. The SG found on natural coral reefs is about 1.024-1.026, and they've had a few million years to acclimate themselves to it lol.