I've got a question about Durso standpipes. I've got a reef-ready tank, which I recently moved into a new apartment. Upon setting it back up, I'm getting some small fluctuations in the water level in the overflow corner. The problem is that its a bit noisy, the water level will rise slightly (in the overflow corner), then fall rapidly, resulting in bubbling-gurgling sound from the sump.
The air intake on the top of the standpipe is clear, so it is able to draw/vent air as needed.
I recall when I first set my tank up in my previous apartment, that it did the same for a while, then eventually settled at a stable level and stopped the fluctuation and noise. Maybe it will do the same again, but I wanted to go ahead and ask because it seems like it shouldn't do it at all.
Under the tank, I have the hose running from the standpipe into my sump, with the other end of the hose under the water (see attached diagram). That should be OK, right? I don't want it above water, as that would be much more noisy, but if it NEEDS to be that way, then so be it. I've had successful, stable water drainage with this same setup before though. Any ideas what could be causing this fluctuation soon after setup? Is that normal?
* NOTE - obviously, the diagram above was whipped up quickly... its not exact by any means... e.g. the water level in the overflow corner doesn't drop below the bottom edge of the horizontal section of the standpipe, I just wanted to give a visualization of approximately what is going on