What are the floor dimensions? If it is roughly the size of a 10 gallon, just shorter, I would say a maximum of 1:5, but expect to clean at least once a week probably 2 or 3 times a week.
It also depends on the bedding you use. I house mine in a rack using 12qt Sterilite tubs which are roughly the same floor dimensions as a 10 gallon aquarium. I use aspen pellets with aspen shavings and toilet paper for nesting. I can usually go at least two weeks with a 1:4 and about a month with a 1:2 before I need to change the bedding.