Okay, I've only owned bettas for a year now, but here is what I have learned.
1. Generally disregard any 'information' given to you by employees at LFS and petstores. Some are knowledgeable, but often it is not worth your time trying to cherry pick through them. It's great to see someone doing research before purchasing, so pat yourself on the back for that
2. All of my bettas are active fish that like to have their own space to patrol. 'Space' is not a 1/2 gallon bowl with one pathetic plastic plant. My minimum tank size is around 3.5 gallons (I think it measures 31cm x 18cm x 24cm), which leaves room for lots of live plants, as well as a heater and a small filter for water circulation.
3. The three most important things for your betta are:
- A good brand of heater that has an inbuilt thermostat and doesn't simply heat the water above ambient room temperature.
- A good brand of dechlorinator that neutralises harmful chemicals such as nitrite and ammonia (Prime is the best for this)
- A liquid test kit for ammonia and nitrite at the very least. Unless your fish is something highly sensitive and requires a specific pH, fish can adapt to a pH that is 'too high' or a pH that is 'too low'. If you get your water tested from a petstore don't settle for 'good'. Ask the exact levels of ammonia, nitrite and nitrate. If they can't tell you, or suggest you need to use pH up or down because your pH has to be 7, consider that whole exercise a pointless waste of time.
4. Cycling. No this is not something you do on a bike. Rather it's about establishing a colony of beneficial bacteria in your filter (this is where 99.9% of them grow). Never rinse your filter media out in tap water or change it out because it looks dirty. You will have effectively killed your bacteria and crashed your cycle.
It's a fairly complex and lengthy process, and I wouldn't bother attempting it on anything smaller than 3 gallons. Essentially, the beneficial bacteria need a constant source of ammonia (provided by your fish as well as any through rotting plant matter and feces), which in the end, is converted to the safer chemical, nitra
This doesn't mean you should ease off water changes and let your ammonia reach anything above 0.25ppm to speed the whole thing up. This will stress or kill your fish, and it is pointless, since the bacterial colonies can survive on trace amounts of ammonia your test kit can't pick up. Nitri
te is even more deadlier as poisoning can occur fast and it damages the blood of affected fish. Nitrate, the end product of the cycle, is safe in levels up to and above 40ppm. It is removed from the tank through water changes.
If you want to know about cycling, you can do a google or even forum search for more info. Basically it is ammonia in and nitrate out.
5. Water changes in small tanks, are not something that can be done bi-monthly. Try like twice or sometimes three times a week. A quick search of this forum will provide you with all the information you will need on how to perform water changes and what equipment you should/might need to use.
The most common problem I see on the emergency part of this forum is people not performing a suitable number of water changes for the size of their tank. There's no need for anything to go into your tank except for clean, dechlorinated water. This will keep your betta healthy and alive for longer than any other chemical or medicine would.
Hope that helps you out. Bettas and fish in general are addictive. If you start assessing every flat surface of your house as a possible tank stand, you may just have a problem.