Question
We have a quite powerful underwater pump in our outdoor pond. We were advised to switch it off during the winter which we have been doing.  Today, as the weather is warming up I decided to switch the pump and filter on but then I noticed that we have lots of baby fish of varying sizes and colours.  Do you think it would be safer for the baby fish if we leave the pump off or would that cause more damage to the adult fish.

Answer
Dear Sandra,

Thank you for your question.
The answer is somehow difficult to answer exactly from A distance.
However in most cases, if pumps are running the filter system, I recommend in to leave them on during the winter, however if possible in lower capacity.
In your current question you need to know if the pump capacity is that large and maze are that big that the risk exists that the little fish will go trough...
Also, you need to check if there are still areas where the fish can hide without fast streaming water, so they are able to find spots where they are safe and relaxed.
If these places are available and the mazes of the pump are small, I guess the risk is more minor.
Please bare in mind to watch the fish closely the first minutes, hours and days to ensure their safety.
As days will become warm I advice to have pumps on to aerate the pond.
Hope this helps.
Please do not hesitate to contact me again if more questions arise.

Kind regards and happy pondkeeping,
Raf