I focused on power and performance - it is important that the pump pumps the entire volume of water in the pond at least once every 1-2 hours. Be sure to pay attention to energy efficiency and noise level - I chose a model with low energy consumption and almost silent operation, and now I enjoy the silence and clean water. It is better to take a body with protection from overheating and blockages, especially if there are fish in the pond. Do not skimp on the brand - it is better to buy a reliable pump once than to suffer with a replacement later. I ordered mine from a trusted store, received a guarantee and excellent advice.