The roman Pantheon with a different base, meant to be filled with weights to keep it underwater. You can fill it with anything and the just slide the Pantheon into the base. No need to glue anything (unless you want to).I recommend filling it with plaster, but anything with weight that fits there works.

I recommend using PET-G for aquariums. ABS can have dangerous chemicals and PLA degrades quicker than PET-G. PET-G and PLA are generally safe for aquariums.Be sure to confirm the filament is free of harmful additives (e.g., BPA, phthalates).After printing, wash the object thoroughly with water and mild soap to remove any residues.Let the print sit for 24-48 hours after printing to ensure all volatile compounds have evaporated before submerging.