So sorry this happened. That sucks majorly.
Double check
where it's leaking from; While it might seem like the head gasket itself, it's often from the weakest part of these filters, the hose adapter:
I've never had an issue with biomaster filters EXCEPT one time when I broke this part.
It's cheap to get a replacement on Oase's website if it turns out to be the case for you. It is the most broken, and most replaced, part I believe.
What I mean by
where is that when the tubing adapter is broken (usually on one of the two underneath 'stubs' with o-rings" it actually still leaks out of the filter head gasket somehow.
I did this recently on my latest stand build. I actually built a lip into the bottom of the stand, sealed it all with waterproof caulk around the corners, then tons of layers of white latex paint:
View attachment 10390
(hard to see in the photo, but the black bar on the bottom is raised about 3/4"-1" creating a "tub" in the base that is 100% waterproof.
I also have not one, not two, but THREE water leak detectors 100dB:
View attachment 10391
They are $8 per detector, in packs of 5, and will wake you in the dead of night when there's a leak. Ask me how I know!
Hope any of this helps, sorry for the troubles lately!