What is the right pump and filter should i choose

I have kept gold fish for years. I have had different filters and air stones etc. Gold fish can gulp air, so they don't need a lot of filtered or aire enriched water. The biggest killer of my fish is me. I have a tendency to over feed them. You might want to try feeding them less. I also learned they like corn and peas. Good luck with your fish.

The petshop is right when they suggested a filter. It's especially important with goldfish which get large, are messy and need big fish tanks. The size of the tank dictates how big the filter should be but some good brands of filters are Eheim and Fluval. I use mostly Eheim in my tanks. The turnover rate (the number of times the aquarium water is replaced per hour) should be 5-10x the size of the tank (e.g, for a 10 gallon tank the turnover rate should be 100 times per hour). The more heavily stocked the tank is, the higher turnover rate.