Nice and Easy
Fish keepers, especially new ones, can find it very frustrating setting up an aquarium and stocking it with fish. Especially when some retailers, ourselves included, seem happy enough to take your money for tanks and equipment, yet appear reluctant to sell the fish you want to stock it with. However things are seldom as they seem, and any good aquatics retailer can explain why this is "for your own good" ... !
New fish keepers have at least 4 factors working against them, excited impatience, new equipment, lack of knowledge, and indeed nature itself. The first is easy to understand, you've just bought a fish tank so obviously you would like to keep fish in it, ... now, ... TODAY.
The second, new and possibly unfamiliar equipment, needs to be set up and tested. It also needs to run for a few days to 'settle in', reach the correct temperature and allow the new water to de-gas.
The forth, Nature itself, is totally beyond your control, but lack of knowledge, (No.3,) hides the dangers of rushing into overstocking you tank too soon. Natural bacteria which filters the aquarium water takes time to establish, 6 - 8 weeks, and adding too many fish at the start simply pollutes the water and kills the inhabitants.
Things can be further complicated by your choice of fish. Some are simply too sensitive to water quality to survive the 6 - 8 weeks needed for the filter to cycle, while others need specialist feeding, such as bloodworm, which can overwhelm an immature filter system. Some are simply incompatible tank mates, but the beginners lack of knowledge leads them to overlook this potential problem.
So wither you buy your fish from us, or from someone else, please follow advise and take things nice and easy. A few hardy peaceful fish to start with and build your stock up slowly. Keep you tank and equipment clean and get into the habit of small regular water changes, and most importantly, DON'T OVERFEED.