Why do Instant Ocean Reef Crystal instructions indicate salt should be mixed to 1.021?

[NatureGuy]

Hey all, I’ve been using premixed salt water form my LFS for the last year or so. This water is at 1.021. I have read that ideally it would be at 1.024-1.026 with 1.026 being the norm.

 

For this reason, I’ve decided to start mixing my own salt; however, the instructions on the bag seem to indicate  that 1.021 is ideal. This is left me wondering if I’m missing something. Could anyone shed some light on the situation. I’ve heard people used to keep their tanks less salty, is this the cause of the discrepancy? 

[Sturgi_0225]

I believe it’s the difference of fish only system 1.021/22 vs reef coral/ fish 1.026

[mcarroll]

6 hours ago, NatureGuy said:

Hey all, I’ve been using premixed salt water form my LFS for the last year or so. This water is at 1.021.

Pretty odd to sell watered-down seawater these days.   It used to be thought that low salinity would prevent the spread of parasites, or even kill some parasites....generally speaking, not the case tho.  (A freshwater dip is 100% more effective and takes only 5-15 minutes or so.)

 

6 hours ago, NatureGuy said:

I have read that ideally it would be at 1.024-1.026 with 1.026 being the norm.

Most folks keep their tanks at 1.025 ± .001.  Anything in that range is probable "ideal".  (Oceanic seawater concentration varies over a wider range.)

 

6 hours ago, NatureGuy said:

For this reason, I’ve decided to start mixing my own salt; however, the instructions on the bag seem to indicate  that 1.021 is ideal. This is left me wondering if I’m missing something. Could anyone shed some light on the situation.

Achieving the gallonage the product claims (eg "200 gallon box") requires a particular s.g. target.  It's just marketing, not a recommendation.  👍

 

6 hours ago, NatureGuy said:

I’ve heard people used to keep their tanks less salty, is this the cause of the discrepancy? 

In a nutshell, yes, I think they selected the lowest "salinity standard" in the hobby since it gives them the best (biggest) number to market.  

 

As you note, actually keeping salinity that low is pretty much an outdated standard now.  There are some VERY specific cases where lower salinity is useful, but I'd have to look through a fish disease book (eg Ed Noga's) to recall what it is....nothing common.