Unless you don't want the plate to lift again you would be better off getting the right o ring for it an then just putting a brick on top of it to stop it from moving when the pump stops.
The Dragonfly Pulse surface skimmer
Silicone is best for that.
Just put your hang in it and get all of the stuff out of it.
CRC Silicone is the best type of silicone for rubik's cube
It all depends on you. Silicone are the most popular.
sillicon
Vina-Strip Seal For Garage Doors works great.
Epoxy or silicone will both work.
Is the skimmer plastic? Does it have a black bottom? If so, there is a kit for this. Check out black bottom skimmer repair - search.
100 % silicone.
Silicone is best for that.
You can find silicone rubber anywhere. A trip to your local hardware store will yield the best results. But amazon carries thousands of pounds of silicone rubber on their website.