A 1 gallon is only suitable for a fighting fish. The smallest size that I would recommend for community fish would be a 2ft tank. Anything smaller would be hard to maintain water conditions and would cause the fish stress.

In my opinion, the ideal size for a fish tank is a 4ft. That is certainly the smallest size tank that I would recommend for keeping angelfish in. This is because angelfish have deep bodies and the deeper the tank, the better their finnage can develop. A 3ft tank has the same depth and width as a 4ft tank but angelfish are territorial fish (though considerably less territorial than most other cichlids) and a 3ft tank doesn't give them enough space to establish their own space and that will cause them stress. If you only have space for a 2ft tank then I suggest keeping fish like small tetras or guppies and platies. You have to tailor your fish variety to your tank size.

Your platies died because the tank didn't have a filter. A filter is essential for all fish - even for fighting fish - because the filter removes ammonia and nitrites from the water. An air pump only aerates the water - it does nothing in terms of filtration unless you attach the air pump to a filter. If you don't have a filter in the tank, fish waste and uneate fish food will accumulate in the water and make the water poisonous for the fish. It would be the same as if you lived in a bath tub of water - just sat in it day and night, peeing and pooing in the same bath tub of water then having your bath in that water and after you eat, drinking that same water!!! That is what an unfiltered tank is like for fish.

Filtered tap water is not recommended for fish keeping because the filter process moves minerals which are essential for good fish health. The only alternative to using a dechlorinator is to age the water - leave tap water in a bucket overnight for the chlorine to dissipate from the water.

Cycling a tank is NOT for the water but for the filter. You are supposed to run the filter in the tank of water for 2 weeks, sprinkling a pinch of fish food every 2 days, before adding the fish. The fish food will rot in the water and feed the bacteria in the water which will then breed in the filter. The purpose of cycling a tank is for bacteria to colonise the filter. That bacteria in the filter is what will break down the ammonia and nitrites in the water from fish waste. The alternative to waiting 2 weeks for the tank to cycle is to use a product from Nutrafin called "Cycle" which is a solution of filter bacteria which will speed up the filter colonisation process.