My Roborovski Dwarf Hamster prefers less space

[arnoldshirl]

Explain this to me. I purchased in the beginning a 10 gallon aquarium tank and bought some accessories such as Wheel, House, Water Bottle, Food Dish, Aspen Substrate, Food, Toys and Chew things. I also bought a exercise ball too then.
Please remain in your seats and stop gasping!

A month later after some research I learned a Roborovski's cage needed to be a minimum of 450 Sq. In. by 18 In. long. I measured the tank and it is 20 In. by 10In. by 12In. The overall Sq. In isn't there. However, she didn't seem stressed over this. She would move about and do her Hammie thing. Only time she would jump up and scratch at the glass was when I approached. She never truly nipped at my fingers then, only a few times in the beginning.

Furthering along here, with this knowledge of home requirements, I returned to the pet shop and the largest they had available was 20 gallon. So I purchased it and gave it a cleaning with a safe bio enzymatic formula cage cleaner to rid of any germs or new smell. The following day, while she was balling it around the room, I transferred her entire bedding area and other furnishings into the bigger tank. I allowed her the time to settle in, of course.
Periodically I would check on her, the usual give fresh water and to let her know I was still here (Didn't need her to think she moved completely away). She was behaving weird. She was constantly digging in the corners of the tank and scratching fiercely at the glass as if she wanted OUT! I set up the play pen I got from Amazon and placed in her 'Let's go explore' mug, immediately she darted into the mug. In the playpen she calmed down, played about doing her hammie thing. This behavior went on for several weeks. One day I placed her in the playpen and while she was there I checked the cage for anything that could be causing her to behave in such a stressful way (I learned that behavior is the hamster is stressed). There is nothing wrong with the cage or her things and the cleaning agent used is Safe and highly recommended too.
After placing her back in her home is where she continued to dig the corners and scratch at the glass in the way of 'Get Me out Of here!' I learned she needs Sand for baths. So I purchased a sand bath and sand from Amazon. She didn't like it! I thought maybe it's the sand, so I found this desert blend sand stuff (after all, she is a desert hamster, right?) It is made of ground English Walnut shells and hamster's love nuts! She took to this right away, in fact she would dig through it to where I buried a few sunflower seeds for her to find, give her digging a well worth pay off. She continued showing stress scratching against the glass as well as many days simply sitting in the corners in a pouting, sad way. When it came time to clean her cage again I placed her in the 10 gallon tank because her playpen was air drying from it's previous hose down cleaning (I always do this after she plays in it). She was so calm in this tank. I slowly and carefully added substrate while she was in there. It was like she was being a part of fixing up her home, ground walnut shell sand here...peanut home there...wheel here...don't need that bath house (take it away my dear human!)...dish there...water bottle hang there...toys just throw about wherever you feel...Perfect, now let me stretch out and melt into a pancake onto this desert feeling floor, I need a nap...
My long winded point is my friend, Cinnamon Bun, who is a Roborovski Dwarf Hamster PREFERS to live in a 10 gallon size tank! Now I ask for any of you to EXPLAIN this reasoning!? and what the hell am I do do with this 20 gallon tank that is obviously still not required size for her?