Two of my angelfish paired off and laid eggs on the filter intake tube (don't know why, I have plenty of swords and slate pieces). Anyways, they were impossible to guard and were promptly devoured by my other tank inhabitants. I'd actually like to keep the next batch, though.
How often do angelfish lay eggs?
Should the parents stay with the eggs?
Is there any object I could put into the tank that they would be encouraged to lay eggs on?
About every two weeks
Definitely! It's an awesome thing to watch!
Mine lay eggs on all of the above and even the tank glass
You could try leaving a light on near the tank at night to give the parents a fighting chance but if you can get them in a tank by themselves that would be best. The tank mates always get them eventually. Also, extra water changes will encourage them to breed.
I've heard that the parents should be removed once the eggs hatch, too?
Depends on the parents. Some will eat the fry, some will raise them. Kinda like people, angels have their own personalities. Sometimes it takes 2-3 spawns for a pair to become good parents. I usually remove the eggs after they are wigglers for 2-3 days, but in my case its to prevent other tank inhabitants from eating them.
Take a look at these threads. These kinds of posts/questions come up like once or twice a week. Some of these threads may help answer your questions: