My 9" diffuser from Aquaticecosystems fits down in top of a 5 ga. bucket and lodges about 1/2 way down. I filled it 4 inches with gravel, tapped the diffuser down with piece of wood and hammer to secure it in the bucket. Or you can use 3 or 4 ss screws thru the bucket and diff. housing. The gravel for wt. and pvc pieces thru bottom make it very stable. The bucket channels the bubbles upward and helps prevent stirring up the bottom sediments.