Could you tell me a good ammonia/nitrate testing kit please? Thank you for your advice I will get ten neons to start then ten of another maybe ember tetras.First you have to cycle the tank. You can use the time to investigate what your local shops sell - assuming lockdown allows. If you do manage to look, make a note of all the fish you like, but bear in mind that the fish in the shops won't have stopped growing yet so they'll get bigger.
Once the tank is cycled, make sure there are a good number of plants. Real plants are best but fake ones are OK. It sounds backwards, but the more hiding places there are the more you'll see the fish. If they know there's somewhere to run and hide if that predator comes along, they'll be more confident.
You can get the first shoal once the tank is ready for them, test for ammonia and nitrite every day to make sure they stay at zero. Once you are certain, you can get the next shoal. And again test every day afterwards. It is better to buy the fish as 10 neons, then 10 something else rather than 5 neons and 5 something else to make up the 10. Shoaling fish do better if the whole shoal is bought together.
If at any time either ammonia or nitrite is above zero, a water change is needed to get them down to zero.