Using Aquarium Salt in Freshwater - Testing Salinity

[bjbass]

I read that you can use a Hydrometer or a Refractometer to test salinity levels. I have been treating my 210 freshwater tank with API Aquarium Salt as my smallmouth bass has a little fin rot. I have been doing the one tablespoon per 5 gallons and when I do water changes I figure on about how much water I take out to replace the salt. However, I want to make sure that it isn't too salty or not salty enough to treat my fish.

How do I test this?

My ph dropped from 6.6 to 6, so I think that I may have too much salt in there and it brought it down.

 

[jsoong]

You have to modify a regular SW salinity meter to read in the low salt levels used. I read it somewhere & can't find the article ATM. It involves drilling out part of the balancing arm & then calibrating the unit to read in the 0.1 to 0.5% range.

Another alternative is to buy a TDS meter. That is pricey ($100). But if you measure the TDS reading before & after salting, the difference is your salinity.

If you have access to a laboratory balance (able to read weight to 1/1000 or a gram), you can calculate the density of water by weighing it.

When I salt, I go for a much simpler approach. I calculate the density by weighing the salt & knowing my water volume. Eg. I have 400 liters of water in total in my tank. To get to 0.1% salt (good level for treating fin rot) I would need to add 1g per liter or 400 g in my tank.

When I do water changes, I fill the tank up to the original mark to account for evaporation. Then I change out a certain volume of water & replace the salt in that volume. Eg if I remove 100 liters, i would add back 100 g of salt to maintain the 0.1%

 

[bjbass]

Wow, great information. Thanks so much!!!

I will look into modifying a salinity meter I think, but your method sounds good too. Let me review that and I will let you know if I have any questions.