Just a Silly Question

[clowningaround]

Okay this is gonna sound like a stupid question but here goes. I have a 120 gal tank fish only a the moment. I'm doing 20-25% water changes every 3-4 weeks. topping off with ro/di h2o in between. I add approx. 40 ml. of B-Ionic part 1&2 every day. I've noticed that over the past few days my salinity is creeping up despite topping off with plain h2o. I've been having to drain some salt just to get the salinity back down to 1.023 ppm. It normally runs at 1.022 without doing anything except the usual water changes. Am I being dumb about something or can you guy's tell me something i'm not doing right?

[gregt]

My guess is you have a faulty hydrometer. Do you rinse it well with fresh water after every use? The dried on salt can really affect the next reading if you don't. Swing arm hydrometers are notoriously inaccurate.

[cyberchef]

You also need to watch out that there are no bubbles of air, anywhere at all, on the swing arm. Even the smallest bubble can throw the reading way off. If I test my salinity with my swing arm and it doesn't seem right I empty the hydrometer and then test it again making sure to look for air bubbles on the swing arm.