Originally Posted by gracem2002
if you have any idea which two item(s) out of the three is most necessary : heater, filter, or gravel for a five gallon.
A heater is required. Substrate is not. A filter sustains your nitrogen cycle, so unless you want to do daily water changes (wich will cost more over time because you'll be using a lot of dechlorinator) to remove the ammonia that your fish produce (it's not just from poop. They also axcrete it from their gills) then get a filter. Once it is cycled and you have a healthy colony of nitrifying bacteria to consume the ammonia for you, then you can do a weekly water change instead of every day.
Amazon-Prime: Hydor Adjustable 25 watt heater
Amazon-Prime: Aquatop IF-201 Internal Filter
(this is a great little filter with a spray-bar... you can adjust where the flow is going in these).
Yeah, don't add chemicals in your tank to remove ammonia unless there is a serious ammonia issue right from the source (from the tap). The best way to remove ammonia is with a water change. Otherwise a cycled filter will take care of it, but you still have to do weekly water changes to keep nitrate down.