6 gallon Eclipse Aquarium

It's going to go in my 4 year old son's room. Any ideas on what type of fish to put in? I am looking for 2 to 4 fish.

An algae eater? Maybe a couple of smaller fish for this small a tank? I have a heater for the tank so tropical is no problem.

There are so many fish in the store and I don't trust the opinion of the teenagers working in there who just want to sell me as many fish as they can.

6 gallon eclipse

on a side note, if a fish dies in a tank, does the whole tank have to be re-cycled? Does it have to be cleaned, air dryed and recycled?

I have a betta that has dropsy and looks as if it is going to die any day now, I feel aweful about it, but not much I can do at this point. So I am either going to put in a different fish with some of the suggestions made here or put in another betta.

But I am not sure whether or not I need to thoroughly clean the tank seeing as I have a sick fish. I have no idea what caused it other than about 3 weeks ago during a water change I was rushing and didn't match the water temps very well and the overall water temp change was about 10 degrees lower and took several hours to get the temp back to normal. maybe this stressed the fish and caused the dropsy?

but back to the question, should I thoroughly clean and recycle tank or just replace some of the gravel, plants and do 100% water change?

I know, he looks very bad and is totally pine coned and bloated. The end is near.

but does anyone know whether or not I have to totally clean out my tank before adding another fish? I would like to just replace the gravel and the plants, wipe down the walls and do a 100% water change. This way I keep my cycle. But I don't want to cause another fish to get dropsy.