Wierd water level issue

[danny zubot]

Not sure where to post this one but I noticed something strange about my water level. When I feed Mysis my watere levels raises about .75 inches in the tank. Sump level drops accordingly and my skimmer barely creates any foam! Everything returns to normal about an hour later so its no a big deal but why does this happen? Only after feeding mysis, no other kind of food.

[trilinearmipmap]

Is the mysis partially blocking the intake to your overflow drainpipe?

[danny zubot]

No, its not big enough. I have a 1.5 inch overflow and bulkhead to a 2 inch drian pipe.

[Delphinus]

Well, mysis is fairly oily and shuts down my skimmers for a while. I assume the lack of foam production puts less back pressure on the pump feeding the skimmer, thus the water level rises in the skimmer, and correspondingly, comes out of the tank. When the foam production begins again, it puts a little back pressure back on the pump, the water level goes back to normal and thus the level restores in the tank (notwithstanding any losses to evaporation, or initial foam spillover into the collection cup, or water put back into the tank during the slightly low period by a float valve or float switch and so on).

[muck]

Well, mysis is fairly oily and shuts down my skimmers for a while. I assume the lack of foam production puts less back pressure on the pump feeding the skimmer, thus the water level rises in the skimmer, and correspondingly, comes out of the tank. When the foam production begins again, it puts a little back pressure back on the pump, the water level goes back to normal and thus the level restores in the tank (notwithstanding any losses to evaporation, or initial foam spillover into the collection cup, or water put back into the tank during the slightly low period by a float valve or float switch and so on).
Thats what I was originally thinking as well but, he's saying the levels go the other way though Tony... :confused:

[Delphinus]

Well maybe it goes the other way then, ie., the skimmer has less water in it. Work with me here! :razz:

[muck]

:mrgreen:

[Aquattro]

No, Tony's right. Skimmer shuts down, water from skimmer now goes to tank. As skimmer returns to normal and fills with water again, tank level goes down

[muck]

Thats a lot of water to be only from the skimmer though.. :eek:

3/4" in a 65 Gallon tank guessing its 36x20ish.
Thats at least 2.3 gallons change in the skimmer..?? :eek:

[Delphinus]

The only other thing I can think of is that somehow the fluctuation in the sump level changes the back pressure on the overflow somehow, thereby affecting how it's operating. However, that said, this might only make sense if 1) the outlet of the overflow is submerged (which I don't know if it is or isn't) and 2) the water level RISES in the sump, thereby putting more backpressure on the overflow. A level DROP would theoretically decrease the backpressure. So... OK I'm at loss now. Maybe if I saw the phenomenon in person I could observe other variables but using my imagination, I've hit the wall here. :lol:

[Delphinus]

Ok. The oil in the mysis supercharges the sump return pump, it runs faster, it puts more water the main tank, and the sump lowers accordingly.

Ok I'm just being silly. But maybe there's something to this. I.e., the water properties have changed "just enough" maybe there's less friction and thus the overall flow through that pump is just slightly higher?

Ok NOW I'm out of ideas. :lol:

[muck]

:crazyeye:

[danny zubot]

I'm starting to get it.
The sump is baffled so that the level on the skimmer side, also the drian side, doesn't change. The overflow is a 1.5 inch 90 degree elbow with a DYI strainer that determines the water level. When the mysis is added and the water level rises the strainer is completey submerged. Sump level on the other side of the baffles lowers because a) the skimmer has less air and is more full of water. b) tank level is higher.

I think we're on to something with the fatty composition of the food. Could it be creating a back pressure in the drain like you said above? ie. An oily drag on the water going down the drain, thus decreasing drain flow?

What a wierd phenomenon.

[danny zubot]

Ok. The oil in the mysis supercharges the sump return pump, it runs faster, it puts more water the main tank, and the sump lowers accordingly.

That sounds more plausable Tony, fatty acids coating a drian pipe wouldn't slow down the drain, they would speed up the return pump. I could run an experinement of the flow rate before and after adding mysis to test this theory. Good Job! :biggrin:

[untamed]

I think that the change is happening in the skimmer. Any small change in the water properties changes the volume of water currently in the skimmer. You are basically removing/adding water from the sump/tank by changing the volume of water in the skimmer.

[johnny rock]

actually, the water level in the skimmer shouldn't really change but the bubbles will stop. how much mysis are you feeding? there should be no real change in any level but that is wierd. any amount of mysis getting caught against your ''strainer/overflow'' will change the level. actually, that strainer would worry me a bit. any dead little fish or algea or anything getting on that strainer could cause flood issues no? I had this setup on my 90g [1 strainer] and after a small flood I drilled 2 outlets with boxes.

[danny zubot]

You're right, the skimmer level doesn't change much, just the bubbles. Every time I feed I check the overflow and its clear, which is why I'm still leaning toward Tony's theory about the pump.