Lid, openings and vents
Start by looking at the lid from outside: is it fixed in place, and are there cracks or side openings? A lid that does not close properly lets in dust, sand, insects and light, all of which raise the chance of contamination and algae growth.
Check that vents are covered with intact fine mesh; torn or blocked mesh either invites insects or stops the tank breathing. Do not open the tank more than you need to during the check.
If the lid is broken or damaged, replace it with one suited to the tank type rather than tying it down with any temporary material.
During the dusty season in Jeddah, inspect the lid after each strong storm instead of waiting for the monthly date, because dust gathered on the rim can fall in the first time the lid is lifted.
