hi, im projecting my new aqua-terrarium, its for my 2 years male...measures will be 90x45x45

i want to make this really realistic, so i have a question:

- can i put some backdrop in the aqua part? gravel? sand? shingles? can u give me an help? can my frog risk choking?

- is necessary an aqua-filter? or i just need a pump to move a bit the water?