I have a 1" sea swirl and would agree with Len that I can't hear it above the noise from the other pumps, etc. If everything else is off, then it does produce a quiet ticking noise. I am very impressed with its durability. Mine has been running continuously for 3 years, with absolutely no maintenance. I also have a Tunze Stream (with controller) and must say that the two are not equivilant. The tunze produceds a much broader, less intense flow than the sea swirl. I have about 1100 gph running through the sea swirl and I really cannot place any corals within 18" of it since the force seems to break them loose from their anchor. The tunze produces a much wider stream with higher flow, but less intensity. I do question the 3000 gph (12000l) that they claim. I am not sure how easy it would be to actually measure the flow?? I have also had to disassemble my tunze twice in the past 6 months to remove calcium buildup from the inside which eventually caused it to seize, and luckily, shut itself off. I would highly recommend both and use both.