Wash the glass ALWAYS. When buying a tank, they are usually uncovered and you don't know what may be in the tank. I like to wet it a bit and wipe away wit a paper towel, dumping the water a couple of times and repeat. Add whatever decor you want, gravel, fake/real plants(You want to use silk plants, bettas have fragile fins and plastic is just too hard), any caves or anything else. This is when you want to mess with the layout and chose what is best for you. i suggest having an area where the plants are more dense and maybe accompanied by a cave or resting place, this is good if your betta is scared or wants to rest.
Then fill it up with tap water, this doesn't need to be dechlorinated yet, so just wait on that. If you have a glass tank, I fill to about where the black trim will start.
Also it will really help if you have a gallon bucket for tanks 1-5.5 gallons and a 5 gallon for tanks 6-15. After add dechlorinator, Seachem Prime is probably the best and lasts a long time, get the smallest bottle (It is 2 drops every gallon). You also generally want a filter, almost all filters will need to be baffled to redirect the flow so your betta doesn't get blown around. Try to buy something that doesn't use disposable cartridges, if you do don't replace them unless they are falling apart. Also you need a heater. A good rule of thumb is 5watts a gallon, so a 5 gallon you would want a 25w heater, adjustable is much better, but preset can work, the tank should be 78 (Get a glass thermometer).
Different tanks require different maintenance, I can tell you a 5 gallon is much easier to maintain then a 2.5 gallon. A 5 gallon would only need a 50% water change weekly, a 2.5 would need 2 50% water changes a week.
Some other things to consider, a gravel vacuum (makes changing water easier and gets poop out of the gravel) and a stable source of food. The best is pellets, flakes are harder to feed the correct amount. I suggest either New Life Spectrum betta pellets or Omega One betta pellets, other brands use fillers, you want the best for your betta! Frozen (not freezedried) bloodworms can be given an occasional treat, once a week. Most pellets I would feed about 5 daily max. I stopped feeding my fish 2x a day and I will usually skip a day here and there, it is good for them and will also cut back on how much waste goes into the water.
Last edited by kfryman; 11-06-2012 at 10:16 PM.