It probably does, but not enough to be concerned about. I empty the collection
cup on my skimmer every 3 to 4 days, to clean it out. That probably is 2 cups
worth, total.

However, if you have a skimmer that is external to a tank and sump, it can
overflow lots of water if conditions are right for it, and a tank can lose
gallons and gallons of water. An Automatic Top-Off device doesn't know the
difference, and will add more water until the float switch shuts it off. So if
there was a 50g resevoir of fresh water or kalkwasser, you should understand the
disaster that is waiting to happen.

Better to have the skimmer in the sump, so if it overflows, it dumps the water
right back into the system and avoids losing any fluid.

Marc


David McKay wrote:

Does the skim from the protein skimmer contain salts from the tank water?
Just wondering if when topping off the tank with pure water I need to take
in to account the waste the skimmer has produced.

Thanks!

Regards,

Dave.

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