This is what I do for angelfish eggs. I remove the slate, sword leaf, pipe, or whatever from the tank all together. I put the eggs in a bucket with half tank water and half fresh water and dose that with methylene blue. Instead of a bucket you could use the extra tank. Add a filter without carbon and a heater to the bucket/tank. Wrap some filter floss around the intake tube of the filter to slow the flow rate and make sure no eggs are sucked up.
Next, wait. Observe the eggs twice a day and remove the fungusy ones with a good pair of tweezers. In my experience they will get fungusy no matter what you put in the water. The fungus will spread do adjacent eggs if you don't remove them.
The eggs will start wrigling a few days later. You will see little tails protruding from the eggs. At this point start doing 25% water changes each day to get rid of the methylene blue and keep the water pristine. Make sure the water paramaters match.
After a few more days the fry will become free swimming. Feed them baby brine shrimp or microworms if you have them, if not, try to grind up some flake and throw it in there. Keep up with the water changes. Eventually you will have a bunch of angelfish that you have no room for and that the local fish store will not want.
Enjoy!