Well, let me give you a bit exp insights when it comes to purchasing hobby equiptment [I've been in the fish hobby for over 20 yrs]. If you plan on being in the hobby for any length of time, and most do plan on staying with it else they wouldn't go thru the expense to begin with, then you will be upgrading your system. I can assure you that if you are in the hobby 2 yrs from now, you would have gotten a larger tank by then, or you will be adding additional tanks. Thus, the way to look at equiptment ALWAYs, is as a long term investment that pays in the long run. Get the best that you can afford...even if the expense does not seem justified at the moment. Down the line, the better equiptment will pay for itself with the use you get out of it where the cheaper stuff will just be ditched once you realize that you want and need to do better then just get by.
That said, if you can not afford the $70 then you should get a good quality hydrometer. The kind that has a tube that you put tank water in, and then float the hydrometer in the tube. You must find one that will read lower salinity readings if you are going to use it for hyposalinity. Many hydrometers do not do this.
