I actually have to agree, the Grotube is really great when it comes to viewing the colony. The flat top and the shallow tapering chambers means the ants can find a place to get comfortable that is ideal to them. The shallowness makes viewing them up close and personal very easy. And it is great for reuse, the water reservoir lasts quite a while. Considering it comes with a bajillion bells and whistles does add to the value.
However, I still think a test tube for your purposes is more than adequate and way more afordable. All you really need is two and you can cycle between them well. The water reservoir in a test tube lasts a long time and even if it gets moldy, all you'd have to do is attach the new test tube and let your ants move into that one. And at the size of your ants, a test tube setup would last you a very long time before you would need to invest in a real formicarium. I would reccommend this above all because it will take your colony some time to grow into needing a formicarium and by then, who knows what crazy awesome products are going to be on the market by then. I know Byformica is working on some new modular acrylic designs that I'm pretty stoked for. Also AntsCanada has mentioned to me that he's got a whole new line of products coming up. I don't keep in contact with TarHeels so I can't speak for them.