^^ keep a low end piece around for such occasions of a questionable visitor, or just make sure they are supervised or assisted. I've been trying to decide which glass should be my main driver, looks like that broken piece from above^^ is roughly the same size as the showerhead Lev bubbler I have, so maybe a bit too small. I have the cracked GBD FC bub (no logo) that has more weight and size to it, should work great, as well as the return of my fixed lil'mona soon (hoping it gets back to me in one piece) which will be interesting to try after it being gone for so long. I'm getting quite the damaged glass collection over here.
in any case, I imagine it will be good to have as solid of a piece under the Sub as possible.
I am curious to see how it behaves in water vs no water. I sure like making those bubbles stack.