I am working on a build for a fiddler crab tank, and I can't seem to get the salinity right. I feel like my hydrometer (which is the kind with the moving dial) might not be working properly. Let me give you an idea of what is going on.
The salinity should be around 1.008 for fiddler crabs. The tank is a 30 gal
, but less than half is filled with water (I'm doing half land, half water for the crabs). I'm guessing it has about 10 gals of water in it. When I first put water in I put a little less than half a cup. It's hard to determine how much since the instructions on the salt are for salinity of 1.022. After waiting a few hours I tested the salinity, which read at 1.013. I did not do anything, but waited until the next day to re-test. The next day the salinity read 1.004. I don't really understand how it could change so much in one day... But since I'm new to this I added some salt (probably about 1/4 of a cup). The next day I tested it and it read 1.002. So I feel like something is going on with my hydrometer. When testing my tap water sometimes it says it has salt, sometimes it doesn't. I know that there are bubbles in it at times, and that messes up the reading.
So basically I need a better understanding of how these things work, or if I should take it back and try purchasing another. I don't think the hydrometers that just float in the water would work, since the water is not very deep. I'm also not spending 50+ bucks on something else to test the salinity, because I'm not made of money.