To make an egg protector for your Oscars you will need the following
Piece of glass 9"x9" , 8 coke or pop bottle tops, 4 self tapping screws, some rigid plastic neting (hole size about 1/2 inch) you can buy this from garden centres, 4 small squares of plastic 1"x1".
First drill a small hole in 4 of the pop tops in the centre so that the self tapping screws will go in. Then, silicone a pop bottle top in each corner of the glass with the open end face up. Next, silcon another pop top on top of each one on the glass,open end face down. This should form a little barrel in each corner. Whislt the silcone is drying cut out a piece fo the rigid plastic netting to the same size as the glass. When the silcon is dry place the square of net on top of the pop tops. Take each of the small plastic squares and drill a hole in them place each one over the net lining up the holes and screw in the plastic this will hold the plastic net in place. finally Place a small blob of silicon on top of each screw to seal it. Leave overnight to dry.
When you need to use the egg protector place a net in the tank so that you can gently drive your Oscars back with it. Whilst you are doing that place the protector in the water next to the slate with the eggs on it gently lift the slate up and place it between the net and the glass and move the whole thing back to where the eggs are. This sounds complicated but its not.