Although chlorine is the least expensive, most convenient and most effective sanitizer for your pool water, there are other options out there. Bromine and Baquacil are the two most well known.
Bromine is mostly used for spas or hot tubs, so it is not recommended for use in your Intex pool.
Baquacil is similar to hydrogen peroxide, and is designed for swimming pools. Some users are quite happy with it, however it is much more expensive than chlorine and you can only buy it from a local pool store. So if you run out of a chemical over a holiday weekend or after the pool store closes, you are out of luck. Also, many users have reported that a baquacil pool is easy to maintain for a year or two, but it eventually will become contaminated with algae and once it does it is very difficult and expensive to recover from. Baquacil advertises advantages such as no smell, no discoloration of clothing, and no burning/stinging. However, a properly balanced chlorine pool will also not have these problems. If you have a baquacil pool and want to convert to a chlorine pool, the process can be difficult and time consuming as the two chemicals are not compatible. Essentially, you will need to add chlorine to the pool until you hit shock levels and then maintain the chlorine at those levels for a few days. The more often you measure & add chlorine, the faster the process will go. Note that your water will turn a very, very ugly shade of green during this process, it will look terrible, but do not panic, it will eventually clear up.