also, I have had plusing xenia before (a couple of years ago) and never noticed any overflow when I had the xenia. Plus there are lots of people out there with xenias. You'd think that this would be a rampant issue with xenias?

No worries, it's a big thread to read through ...

I use carbon and gfo in 2 TLF 150s, and change each @ 4 weeks, 2 weeks apart

I agree it should be a noted issue, but I'm kinda at a loss to figure it out

Causes of random skimmer overflows are, with a constant water level;

Blocked air intake
Plugged or dirty/buildup in venturi

Anything else ?

Back to my observations ...

My foam head collapses at about 5 or 6 days after a WC, and does not recover until after another 10% WC

I've tried turning the skimmer off during frozen feedings; turning it off for a 1/2hr when it's acting up; total cleaning when it's acting up

I haven't had my hands in the tank for many weeks, and am very careful about what does go in
I'm at a loss here, so hence the weird questions about coral warfare and possible 'stuff' in the water building up causing my foam to collapse over time

Some more info ...

When I said it collapses, I was serious
Skimmer is currently 'bubbling' as if it was a mix of vinegar and baking soda, without the overflowing of the volcano
No foam at all, just lots of bubbling

With it's track record, if I were to turn it back up right now to get some foam, by morning it will have filled the cup, or overflowed into the sump

Interesting.... Mine has been doing that a few times lately, too. I have been adding new corals, though, and I think all the gluing, new frag plugs, cement and putty is what has been doing it. I just make sure that it is dialed low enough so that it doesn't overflow. Just the same, have found the cup nearly half full a couple times, even with the skimmer level down low.

Ya, probably your issue is all the glue/epoxy etc and you putting your hands in the DT while you're playing with your new corals

I've considered all the times I've put my bare hands in the tank, and all the times I've added new corals, and it still does not equate to my skimmer overflowing ACK

You've all been sleeping ... I'm just going to bed

Please add your thoughts and I'll read them as soon as I get up :mrgreen:

Some more long shot ideas...

You say it happens about a week after a WC. Maybe some build-up of something in your water, or a depletion. Not sure if your parameters vary in that time, but might be some other things that you don't measure, maybe some contaminant coming from somewhere.

Not sure what you do for ATO. Do you use a separate container that maybe has some kind of build-up and needs a good cleaning?

Good thought about my ATO
There may be some bacterial buildup in there I need to clean out

Wow do I feel like an arse
I bought this skimmer used and had no idea what the inside of the venturi was supposed to look like
Skimz used 2 different colors of plastic, so the build up of calcium in the venturi looked normal to me :doh:
Add a piece of food, algae or a small snail and overflow was imminent

A clean with vinegar and some elbow grease and wouldn't you know it, it's pulling some serious nog again

Think I'll have to change the location of my drip :smile:, and my weekly cleaning of the cup will now include the venturi