Can't hit 2.5feet bottom.
With the max extension can hit about 2 feet.
Top part cant submerge in water. There is a marking on the device.
For 2.5 feet tank.. guess gemsurf have a better equipment to hit 2.5 feet tank.
What I meant good was I will stir up those detritus during changing water.. so my tank water level no longer 2.5 feet. Then I will hang this device and let it continue vacuum for little while. Then will repeat the process of stir up the detritus until mostly clear then only I top up the water.