Low specific gravity, please be very specific with advice

Running wet would be where the skimmer cup is collecting a lot of water. This would affect salinity because it means you'd be losing saltwater whenever you added freshwater.

Do you have a lot of salt creep? That could be another way that salinity was decreasing. How about the possibility of leaks?

I'm guessing it's mostly a hydrometer issue, but you might want to check the above as well.

 

Thanks so much Zechenia normally there isn't much water in it, but I was having an issue with the skimmer yesterday, since that's when I had the significant drop, I think you're right. I don't think I have any leaks, there is some salt creep, but doesn't seem to be a lot I will double check both, thank you again. OH! what do I do to prevent salt creep besides setting my skimmer lower? Most of it seems to be on the back of the tank just below the rim of the lid. I would assume from splashing while going into the bioball part of the filter based on location. I did recently install a more powerful water pump, could this be the problem? Now that I think of it, I did do this sometime around the same time all the salt probs started, can't remember exactly when though.

 

A little salt creep is normal (it took me a while to figure out what "normal" salt creep is). On a 29 gallon I'd think you'd need a lot of salt creep to notice a drop from 1.024ish to 1.020 (once again, if it really did swing that much compared to it being because of the hydrometer).

I have a 28 gallon bowfront w/hob refugium. And I've never noticed a swing from saltcreep. I think my water changes are enough to keep up with it.

 

Please post a picture of your setup so we can see whats going on. Most hydrometers i've used have been fairly accurate. I don't use them anymore since refractometers are much better at testing salinity.

seems unlikely that the salinity/specific gravity would fluctuate so much unless your room temperature is at 90+ degrees.

Either way your fish/coral wouldnt die if it went up or down a bit. My best guess is that your hydrometer is faulty or hasn't been cleaned properly.

 

It was definately the skimmer. I had it adjusted as low as it would go and still bubble just over the top of the tube before adding the colection cup. I would only end up with maybe 1/4 inch of water in the bottom, but after leaving it off, I had NO overnight drops in salinity for 3-4 days, so I removed the skimmer. Have not had a problem since. Thanks for the help guys

 

What a fantastic troubleshoot