Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
Long startups are normal. Water soaks into the diffuser while it's off, and with water being so much more viscous than gas, it takes a while to force it out of the incredibly fine pores.
Long shutdowns are also normal, especially if you cranked up the pressure, while the gas accumulated in the tubing (and especially bubble counter if present) bleed off.
The diffuser should never truly be putting out a massive amount of gas. Only a massive amount of bubbles, so fine they look like smoke. Great diffusers, very efficient.