Fish tanks are pretty but they do take regular upkeep.
We got ours at Petco and the staff in Allen was quite knowledgable. We've also done a lot of business with Plano Pets and recieved great advice.
We bought a 29 gallon tank kit, the ready made filters to change monthly, food, algae disc, stress coat, net, stand for the tank, plants and shelter areas. We spent about $300+ on startup.
You do have to have water changes regularly (we do it about once every couple months or when it looks like it needs it)This is when you take out about 1/3 of the water and replace. (Use the water you remove for your plants....works great as a fertilizer! My roses were beautiful!)
The tetra website site is very helpful.
We use spring water and we ended up using plastic plants because the live ones would not live in our tank.
We have 2 red tail sharks that have done well, tiger barbs are aggressive and we only have 1 of those now, neon tetra's are pretty, swordfish are pretty, guarami's (these get aggressive too). The staff at Petco or Plano Pets can tell you what fish get along best in a semi aggressive tank. The Placo (algae eater) eats at night and keeps the tank pretty clean.
Good luck with your tank!