9 months, no skimmer problem... now what???

I have the Coralife Super Skimmer 125 setup as HOB on my 55 gal.
It's be working flawlessly for the past 9 months, but recently am having issues with it.
I empty/clean the cup every week or so.
Whenever I replace 2-3 gallons of top off water, dose Ca, Mag, or Alk, or do a w/c I always watch the the skimmer for an hour or so while I'm watching TV to make sure it's dialed in correctly (not pumping out water, but still producing foam - basically optimal dry skimming).

Last night, I fed the fish and was getting ready to do a w/c and scrape the front glass.
I had 4 gallons of sw mixed in a bucket, ready to go, and was only just removing my tank lids to wipe them down (fresh water, no windex, and I prop them open for air exchange). I had not even removed any water, when I started hearing that sound...

So I look over the top of my lights and the skimmer cup is nearly full, and water is escaping down the drain line into the overflow jug.
I hadn't dosed any buffer or Ca yet, and didn't take any water out. So why did the skimmer just go nuts for no obvious reason?
The pump was working, the pump inlet was unobstructed, no meds in the tank, water chemistry and temp did not change...?
So I did the w/c (rodi and IO mix), replaced carbon, replaced phosphate media (seachem) and rinsed sponges in my Fluval 305. Scraped the glass, cleaned my lids. Added Mag (~1450 ppm)- and watched end of Gone in 60 Seconds.
Later I added Ca to bump it up from 420 to 450 ppm, then waited while watching Casino and keeping an eye on the skimmer.
I dosed baking soda a little while later to get it up to 12-13 dKH.
Made sure the skimmer was working right before I went to bed, then checked it this morning and seemed fine.
next post....

 

So tonight I'm watching House, everything is cool with the tank.
Then I'm watching Fringe and right at 10 when it's over, I noticed (heard) the skimmer is going nuts over flowing again. It filled up the 1 gallon overflow jug, and starting leaking out into the 5 gallon (just in case) bucket I have that in - plus it fits perfecty in there as a place to store the extra bucket.

All corals look great. Water parameters are perfect. What could be wrong with this skimmer?
I don't want to hear that it's a POS and should have bought an eheim or bullet or whatever. Something else is wrong.
I'm going to disconnect the pump and clean it, remove the bits of coralline off the inlet strainer, and check to make sure the air inlet and check valve are working right.
If it's not any of those issues, does anyone have any ideas?
Thanks, '
be back in a few...

 

i have the larger version of that skimmer 220 or something i think and i've noticed that if i move the pump intake even a little{the piece that connects to the venturi it can make a dramatic difference is bubble production and as a result the height of the water.. is this maybe what happened?

 

I prop it open on the front corners to let air flow through.
I see what you're getting at with the air/oxygen exchange, but that's never been a problem. One power head makes the surface pretty turbulent for gas exchange, and I even tested pH last night (just before lights out - 8.2-8.3 very normal). Also 0 nitrates. And that was before the w/c, and just after I noticed the skimmer going nuts last night.

 

You feed any kinda coral food or frozen that could have made it go nuts?

 

Nope, that's not it. The skimmer angle is secure, and you know that 1/2" tubing is tight as a mofo on the pump outlet and skimmer body, so the height of the pump doesn't change. If anything, water evap from the tank would lower the water level, in which case the skimmer would need to be turned up - it wouldn't be overflowing. Thanks for the reply.
Going to check out the pump now. Any other ideas?

 

Never happens. Only once I saw it do this and noticed that the little piggies (tangs) ripped the entire piece of seaweed off the clip. It got sucked onto the skimmer pump inlet, resulting in the skimmer suddenly overflowing the collection cup.
Going to check the pump, inlet and air line now.

 

Ok,
Cleaned everything.
The inlet strainer was a little more clogged up with coralline than I thought, don't think enough to be causing this problem.
The air inlet is ok.
The inside of the pump and needle wheel were very clean.
Putting it back together now...

 

Did you change brands of frozen food? Is there any relationship between feeding and the time you are seeing the skimmer production change?

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