Concentrated saltwater?

[Myka]

I've heard recently on a few occasions where people premix the saltwater extra salty with just a powerhead and no heater, then dilute and heat before a water change. I know you're going to get precipitation at a certain concentration. I'm not wanting to do this weird premixing, though it has me curious about the affects. I know some salts with high alkalinity are prone to a small amount of precipitation just from the powerhead heat, but I'm curious at which salinity (or SG) would the concentration start to cause significant precipitation and have potential issues for the tank?

 

[redfishbluefish]

As is, with some salts you get ppt from the heat of the powerheads...or just sitting too long. Red Sea Pro wants you to use their salt within four hours of mixing, presumably from ppt occurring.

Maybe I'm old school, but I'd only mix salt with the full volume of water first. You're paying extra for these "super" salts, why loose some of that benefit from it precipitating out.

 

[Myka]

You're paying extra for these "super" salts, why loose some of that benefit from it precipitating out.

These people are not "super salt" people. They're using IO or IORC. I think one of these people uses H2Ocean.

 

[Downbeach]

Most regular salt mixes, i.e. IO, are already higher in Ca, Mg and alk than natural sea water, the "Pro" / "Reef" types, i.e. RC, RSCP, etc., are even more elevated, so in that sense they are already somewhat concentrated...relative to NSW. So, the more you further concentrate it, the more likely you're going to realize some precipitation. I don't see the benefit in it.

 

[Randy Holmes-Farley Verified Community Expert]

Mixing to hypersalinity is a bad plan. It great accelerates precipitation of calcium carbonate, which will not redissolve.

How fast it happens is going to be strongly depending on the alkalinity and pH of the mix (before and after aeration) and the temperature.

Salt mixes often have a lot higher alk then normal seawater, but normal seawater at normal pH will precipitate calcium carbonate and magnesium carbonate at least by the time you get to a specific gravity of 1.14 (which is about 50% water by weight). Calcium sulfate will also begin to precipitate at higher concentrations.

That said, most mixes (such as IO) produce some calcium carbonate even when mixing normally, so mixing hypersaline will only make that worse.

 

[Myka]

Mixing to hypersalinity is a bad plan. It great accelerates precipitation of calcium carbonate, which will not redissolve.

How fast it happens is going to be strongly depending on the alkalinity and pH of the mix (before and after aeration) and the temperature.

Salt mixes often have a lot higher alk then normal seawater, but normal seawater at normal pH will precipitate calcium carbonate and magnesium carbonate at least by the time you get to a specific gravity of 1.14 (which is about 50% water by weight). Calcium sulfate will also begin to precipitate at higher concentrations.

That said, most mixes (such as IO) produce some calcium carbonate even when mixing normally, so mixing hypersaline will only make that worse.

Yeah, I hear you. That was my concern. I think these people are only mixing to about 1.040 and mixing with no heater, then when it's time to do a water change they add heated water to dilute and heat. I don't really get it, why not put a heater in there? Some people are really cheap! I was just wondering if I could give them some advice like, "Ok, but don't go over 1.xxx or you will surely cause excessive calcium carbonate precipitation." I know it's not that simple, but there has to be some limit where it's not going to make much difference.

 

[Randy Holmes-Farley Verified Community Expert]

The limit is going to depend a lot on

time (how long you wait)
temperature
alkalinity (impacted by brand)
pH (which is impacted by brand and aeration and CO2 levels in the environment)

So I can't supply any special level except to remind you that even at normal concentrations, precipitation is often a problem.

All I can say is try it and see how much (if any) solid precipitate forms. Monitoring alkalinity of the settled water would make this clear whether it is a problem or not.

 

[redfishbluefish]

........ I don't really get it, why not put a heater in there? Some people are really cheap! .......

Not cheap at all! It might be counter intuitive, but your friend IS better off not heating their salt until later. Heat reduces the solubility of calcium carbonate, so they are better off mixing with no heater. I would recommend all aquarists mix their salts with unheated water....just plenty of agitation/mixing. Heat the water just before you are ready to add to your tank.

 

[Myka]

Not cheap at all! It might be counter intuitive, but your friend IS better off not heating their salt until later. Heat reduces the solubility of calcium carbonate, so they are better off mixing with no heater. I would recommend all aquarists mix their salts with unheated water....just plenty of agitation/mixing. Heat the water just before you are ready to add to your tank.

Agreed. I don't plug the heater in until the day of a water change.

 

[Myka]

All I can say is try it and see how much (if any) solid precipitate forms. Monitoring alkalinity of the settled water would make this clear whether it is a problem or not.

Yes, I was thinking to do some testing and see if it seems to be an issue or not. IMO, reducing the alkalinity of IO isn't a bad thing (though it doesn't need the calcium lowered)! :lol: I use muriatic acid to reduce the alkalinity of H2Ocean for my own tank.