Have you ever used your refractometer with your skimmer cup liquid ?
I did it when the OP started this post and was not surprised to see 1.015

Umm......no. I've never seen any reason to check the salinty on fish waste. But rather than get in an debate over this i'll just step away and hopefully some other members will chime in and change my thoughts on skimmers causing the salinity to drop. I only have my own experience to go by and nothing to back it up. So in closing you win bro. Sorry to the OP for the minor hijack.

I can't find any articles to back up my thoughts on skimmers and Sg
I'm still working on finding something to back up my thoughts on low Sg for critters

Yeah, 1.023 doesn't sound correct. I have purposely lowered my sg by adding plenty of topoff water before vacation and measured less than that without any negative effects on my tank.

Hey Greg got your PM. :grouphug: :biggrin:

your cup contains tank water in it plus organics. just because it's dirty water doesn't mean it's not salty. those bubbles pop and splatter salty water on the lid and it drips down. unless my logic is off i'm not sure how skimming couldn't to some very small degree affect salinity? and if you're removing a lot of salty skimmate you're lowering your sg.

plus this :biggrin:

Hmmm I recalibrated my refractor checked my tank salinity, it's 1.025. Skimate is 1.015 same as Greg's. I wait until my skimmer cup is full before I empty it. The sg never changes. I also measued how much my collection cup holds and it's 14 cups of liquid and not including the sludge. Thats quite a bit. So you'd really have to take a whole lot of wet skimate out to effect salinity that much. P:lus throw in the 10G of fresh water thats added.:confused: Have any of you brainiacs looked in to this theory at all bout skimate dropping sg?

Taking a fairly extreme case.
Let's take a 90 gallon display with a 40 gallon sump, sump isn't full to the brim and there's rock in the display, so call it 100 gallons actual water.
Say you have an extremely large skimmer cup (14 cups in almost a full gallon!) and it fills once a week with not much gunk and pretty much all water at 1.026.
After one week, your sg would drop from 1.026 to 1.02574, two weeks would be 1.0255, and three weeks 1.0252.

That's pulling a gallon of skimmate a week of what appears to be a relatively unrealistic sg of the skimmate.
I would venture to say that although your skimmate does no doubt contain a small portion of saltwater in it, the design of a skimmer should drain the saltwater and only skim the organic crap for the most part, and anybody running into a significant swing with their sg because of their skimmer, no matter how "wet" you skim, has a serious skimmer malfunction, or the cause is probably somewhere else.

I will totally concur with skimmate being a drain on salinity... The only way it would not contain salt would be if it was distilled :lol: And since I doubt your skimmer(s) are pushing foam near the boiling point, the liquid in the cup has not been evaporated/condensed during the process and thus is most probably not pure water. So salinity is thus decreasing because top-off water is pure and diluting the tank.

Same applies if you are dripping new tankmates -- I always add to the tank about how much I plan to drip out of the tank prior to starting acclimation so that my ATO doesn't run extra and dilute my salinity (which as everyone I have set to a specific level on purpose)

just my opinion but the skimmer is and will continue to be the last thing I look at for SG fluctuations.

Maybe if you were running a 500g skimmer on a 5g nano?????