Although I do like the look of those marina tanks - they are only .5 gallons and that is too small for a betta to be happy and healthy in (depite what petshops want you to beleive. It like us living out whole live in something the size of a bathroom - yeah we COULD but we would not be happy abut it).
Besides it being too small, the bigger issues are
1) can't really be heated as almost all models are too tall to fit in there
2) ammonia will build up and the ONLY way to remove it is with daily water changes.
If/when you can - it is best to upgrade him to something bigger with a heater. It dosen't have to be an expensive setup. Some of my "tanks" are sterelite storage bins that I got at walmart for under $5
it's not the most attractive setup from a human point of view but my fish don't seem to care. Petco and petsmart have those kritter keepers - the largest size is about 2.5-3 gallons and those work well and are about $10.
Or this one is actually a really good deal for a 5 gallon setup - normally I see 5G kits going for at least $50. This one is $30
There is also a 1 gallon kit. I have this one and its not bad - but I wouldnt use the "filter" as it takes up too much space (a 1 gallon is still pretty small but much better then a .5 gallon). Plus most bettas wont care for the bubbles and you still need to do the 2X weekly water changes anyways.
As for heaters, I would NOT get the tetra ones - they don't work too good.
I got all mine off ebay or amazon.com - much cheaper
and my last word of advice - Never trust what any petshop employee tells you! I ended up illing my 1st FIVE bettas because a petco employee told me "if I have a filter, i never need to change the water". Needless to say the ammonia built up and the fish died from ammonia poisioning
I know you didnt come here looking for criticizm of the tank and that is not what I am trying to do. I'm just pointing out what you can do to improve the fishie's quality of life, if you choose to do so. It seems the majority of people on this site came here not knowing how to properly care for their fishie and assumed they liked to live in small, dirty water or they can live off the roots of lilly plants, or beleive the petshop lies. Like I said, I killed 5 before I decided to fins out why they were dying
Edit to add
Be sure to always use water conditioner when changing water :) and if you upgrade, he will apperciate a little cave or castle to hide in and maybe a silk plant too