Here we have a pair of angelfish who every month without fail lay eggs in the same place, on the internal filter in a community tank. Some eggs go white and die, other don't hatch, and after a few days, they disappear. Perhaps they do hatch, but are sucked into the filter.
The male angelfish is in the foreground. The two angelfish take it in turns turning to face upwards and slowly swimming up. First the female sticks a line of eggs, then the male swims over them doing his thing. Eventually, after some hours, you end up with a mass of eggs as you see here.
Eventually they will be moved to a deeper tank with a high piece of slate to breed on. Perhaps some day they will succeed.
I'm sure I left my keys here somewhere...