How do I cover alot of areas?Updated a month ago

Option 1: You can exceed the 1ml per 10L recommendation, and do a large (~70%) water change after that.  

Option 2: You can spot dose on one area today, and spot dose another area the next day. Do this over as many days as you need to cover all areas. Generally a single spot dose will be effective for any specific area. This method is slower but can be used if you are keeping more sensitive livestock.

Old leaves that are deteriorating are big algae magnets. Plants abandon old leaves and focus on defending new growth. Old leaves have limited capacity to recover once they start to deteriorate, and it is better to cut off these old leaves and allow the plant to channel energy to new growth. It is not worth treating all the deteriorating growth with algicide as deteriorating leaves will not recover in the long run even if the surface algae was removed.