questions about h20

[mzlambert]

we bought 20 gallons of saltwater yesterday (4- 5 gallon jugs) we have about 4 gallons left and were wondering, how long does it stay good? can we keep it for a water change or should we just dump it out?
also, how can we test for the salinity of our water?

 

[snakeblitz33]

You can keep it,... seal it up in a container, and then before you use it, aerate it with an airstone or a powerhead and check for the proper pH before your water change.
You check your salinity with a hydrometer - which is the cheap way, and inaccurate over time. But then, there is the way, way more accurate way ... and the best way, which is to use a refractometer.

 

[mzlambert]

thank you snakeblitz33.
as soon as i posted this i saw something about a refractometer. i posted about it in equipment and diy.
i was wondering which would be the most recommended to buy.

 

[snakeblitz33]

Any of them sold for saltwater aquariums... they usually average about $50 and they measure salinity from 1.000 to 1.040... Ones for making alcolhol or dog urine don't measure up to the specific gravity that we need for our aquariums, which is 1.024-1.026 or 35ppm