Aquarium Safe Lubricants

Vaseline is safe, as long as the fish can't get to it.

You shouldn't need a lubricant on an impeller as they're made to quite an exacting tolerance(?)
If you're using a pond pump, say, in a tropical tank, then the impeller will expand slightly due to the warmer temperatures and can then become too big for its housing, but a lubricant won't really help there.
Vaseline on a sealing ring is in contact with the water, which is safe for fish (it's a grease(?) so it's insoluble).

If you're using it on the barrel of the impeller it should stay where it's put. It's only unsafe if fish eat it.

Sorry to resurrect an old thread but my issue is almost the same as this and it would be interesting to know the answer to the last query on here. I am considering putting Vaseline on the impeller but, unlike any other filter I've had, the particular filter has an exposed impeller and so theoretically would run the risk of the fish being exposed to it - presumably, therefore, it is unwise to try? Also, do we know definitively whether or not it degrades the rubber?

Hi Guys,

As I raised this question originally, I have since found, and use, a "food safe" silicone grease I found on Amazon. https://www.amazon.co.uk/gp/product/B00APYQTPQ/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1 I have used this on the O ring on my Fluval 306 motor head and on the impeller with no issues. Only a very small amount is required to "lubricate" the O ring and or the impeller as "a little goes a long way". Hope this is of some help.