You only have to cover the sediment with black trash bags to do the black out, it can be a local area. You can still allow the leaves to poke up. Many folks do not have access to antibiotics outside the USA etc or do not want to use such methods.
Spypet, you need not do that, it's not bad etc, but does not help, simply covering the tank works great and is far cheaper, simpler and works just as well.
No need to make a simple idea more complicated, but I do understand the urge to do so
Regards,
Tom Barr