Knocking noise from sump?

Waters · Sep 25, 2015

I am starting to think I am crazy.....there is a knocking noise coming from my sump that comes and goes....sometimes it is every 10 seconds or so......sometimes not at all.....sometimes loud, sometimes not lol. It is coming from the side where water enters the filter socks. I have unplugged the skimmer and UV without any improvement. I think I "may" have figured it out. I have a normal 100W heater stuck to the side of the (acrylic) sump. Since I have run out of options, I figured I would move the heater towards the center.....the noise seems to have disappeared. Can the heat coming from the heater, against the acrylic, cause a knocking noise??? I know it seems impossible but I don't have any other explanation. It isn't the heater itself, because it was doing it with two different heaters in that same location. That side of my sump only contains two socks and two heaters...nothing moving in there except water.

TheEngineer · Sep 25, 2015

I was thinking heater too, but not from heat. Is the heater bouncing around in the flow? Try moving the heater to a different compartment and see if it still happens.

Waters · Sep 25, 2015

There isn't any substantial flow....heater was connected via suction cups against the side. I even tried duplicating the sound by knocking the heater against the sump....sounds totally different. Almost sounds like ice (or acrylic lol) cracking. I also thought maybe a large snail got caught in the PVC coming into the sock (I have a gate valve controlling flow) and couldn't fit through the valve and was banging around but the sound doesn't appear to be coming from that area either. I have spent hours with my head stuck under my tank examining the sump with a flashlight trying to figure it out lol. The fact that it comes and goes doesn't make any sense....which is one of the things leading me to the heater turning on and off.

runzwithscissors · Sep 25, 2015

Maybe snails? Could be falling into sock and then finding their way back up?

Reefing Madness · Sep 25, 2015

Only thing I can think of, is if you have Live Rock in the sump, you now have a Mantis Shrimp along with it.

twilliard · Sep 25, 2015

Reefing Madness said:
Only thing I can think of, is if you have Live Rock in the sump, you now have a Mantis Shrimp along with it.

That's what I was thinking of. Random knocks or clicks.
They make a very distinct sound

Waters · Sep 25, 2015

The Mantis Shrimp did enter my mind, but my sump is completely bare. That is what makes this so frustrating.....there is nothing there that should be making any noise but I can sit there, listen to it, and pinpoint exactly where it is coming from. Also, definately not snails......my Tusk took care of all of those unfortunately (plus I swap socks every week). I checked about an hour ago and still no noises since I moved the heater into the center of the sump.....although I am still not convinced that was the issue. If it starts back up, I will grab a video of the sump and noise.