What's going on with my overflow?

[ACBlinky]

Something interesting/strange is happening with my tank, thought I'd see if anyone here has experienced the same thing (and if I need to worry)...

Yesterday I was harvesting chaeto, and ended up releasing quite a bit of detritus from the sump into the main tank. I wanted to catch as much as possible in the filter sock, so I decided to open up the ball valve on my Mag 9.5 for a little while to increase the flow down into the sump.

Much to my surprise, rather than the gurgling and slurping I expected, opening the valve from about 60% (where it's been since setup) to 100% caused NO extra noise. No gurgling, no sloshing, nothing at all except increased flow. I could feel that there was much more water passing through the locline, and see that there was more coming into the sump, but even after a few hours I didn't experience any of the ugly noises that were there when I tried to run at 100% when the tank was new.

Everything was torn down four months ago when we moved house, and that included rinsing out all the PVC and soaking the Mag 9.5 in vinegar & giving it a good brush-out to clean any gunk and calcium deposits out. The locline doesn't seem blocked in any way, the pipes don't seem restricted, the overflow is clean (not very much algae buildup on the edge, no detritus/algae etc. in the overflow chamber) and I don't really have any snails or other critters that could get lodged in a pipe so...

Any explanation? Do I need to worry, or is it normal to be able to increase flow after the pipes get a coating of slime etc. ?

[snulma1]

I would tend to agree with the slime build up. I've found that it takes care of a lot of gurgling noise in most plumbing.

[ACBlinky]

Thanks much for the reply

It's strange to see the pump going at full capacity after being dialed back so much for so long, but it seems fine so I'm leaving it - it's not much more turnover, but I'll take every gph I can get!