Opinions Requested - 10 Gallon with Topper, or 20 Gallon L?

[chewyfriendly]

I have two male gerbils who are currently in a 20 Gallon Long tank with a not very well made DIY topper. I am adopting a cat so I need to figure out a better setup that will be cat-proof.  The current one is too precarious, I am afraid the cat could dislodge it and get in. 

One option would be to use the current 20 Gallon Long Tank, and divide it into thirds.  One third would be for their food, wheel, water, and a very small amount of Aspen/Carefresh (1 inch). The other two thirds would be for floor to "ceiling" Aspen/Carefresh/Timothy Hay for them to burrow in. I would use a full tank cover for it, with locking clips. 

The other option would be to buy a new 10 Gallon Tank, and get a real topper for it that locks on and cannot be knocked off. So the bottom tank would be for burrowing, other things would be in the topper.

Can you all chime in with which you think they would prefer?  They do currently like the topper, as well as burrowing.

Thanks!

[blanknote]

Would it be possible for you to upgrade to a 40 gallon tank instead? Not sure where you live, but Petco has dollar per gallon sale on their tanks quite often, and you can also find 2nd hand tanks online.

I know at least of one case where the cat was able to grab the gerbil's tail when it was right next to the bars or a little bit out of the topper, so I'm not sure do cats and toppers go well together.

[catnut]

i'm not sure I understand how you will divide your tank but are you able to get a bought tank cover for the tank you have? I've been able to get used ones with tanks but I've seen them at pet stores. Some cats don't bother gerbils, like my Truffles and she is a rescue, she is soon bored watching them, while others' will do anything to try to get to them. Good luck finding a nice rescue or do you have one chosen?

Tammy