Tunze 9012 Tends to Overflow

[Newms118]

I have been using a Tunze 9012 in my sump and it has been running well down there, except recently the cup has been overflowing despite not being full. I have been dosing carbon (Red Sea NO3 PO4 X) to bring down the phosphates and since then no matter how much I turn down the skimmer, foam will come out the top of the cup (pops the top off). I have tried putting a weight to keep the cap on but then the foam just ends up coming out the 4 holes in the cap. Here is an image to show that the cup isnt full, its just the foam is really thick and doesnt seem to collapse.

Sorry the pic is tilted, issue with the upload.

Does anyone have an idea on how to get this under control?

 

[rvitko]

This is the result of the carbon dosing, the carbon dosing binds the phosphate and nitrate into a skimmable molecule so the skimmer has a lot more to pull out and there is a surface tension change. I would dose much less of the product at a time.

 

[rvitko]

You could also try smearing some vegetable oil on the under side of the lid (not on the part right over the riser tube) the bubbles will pop when they touch the oil and fall into the cup.