nice job, here is mine, it is for a 90 gal
, very big heavy piece (that floats).
i did about 5 layers of cement, then paint, and seal with west system marine grade sealant. problem is, even thou it is full of cement, the foam core will make it float. i should have melted the foam on the inside before sealing it up!!!!!!
live and learn.
so i would imagine yours will float too so make sure to secure it to the bottom or put a very heavy object on top.