Try using a piece of slate, and hatching the eggs in a separate tank (or modified container such as a Rubbermaid bin). Some angelfish also like to lay eggs on a sponge filter - you can get the "XY" sponge filter brand for cheap on eBay, literally just a few dollars including shipping (from Hong Kong).
There is no way the eggs will hatch in your tank! Lots of fish in there who would be happy to eat them. Most likely the angels themselves or your pleco (Sploke is right about your violet goby)
This site is organized a little weird, but has a lot of good info:
http://angelfish.info/
Especially read these two:
http://angelfish.info/frytank/index.htm
http://angelfish.info/spawningslate/index.htm
This is a good site too, the FAQ is short (big text) but divided into 6 parts:
http://www.angelsplus.com/ArticleBreeding.htm
If they spawned once, chances are they will spawn again. You can make sure of it by conditioning the parents - Google conditioning angelfish. Basically, just feeding them some special foods and keeping up on water changes to keep the water as clean as possible should get them going again.
There is a ton of information on breeding angelfish on the net, they are very common fish to breed. So if you read a bit each day, by the time they are ready again you should be prepared! It's a lot of work, but very rewarding. Just make sure you have the space (you will need a large growout tank) and the money to buy the supplies you'll need (the fry will need special foods for a while, they can take crushed flake later - you'll also need something to prevent fungus on the eggs, read about the different things people like to use - Methylene Blue is a classic but will stain silicone seals blue)
Hope that helps
