Pressurised filter UV bulb Newbie

[Mukster]

I just recently fitted a 4000litre pressurised pond filter that has a 9 watt bulb as it's uv light. Is there anything to stop me swapping in an 18 watt bulb instead? Any pointers or warnings appreciated.

 

[Meyer Jordan]

If that is a 9 watt UV unit then the starter/ballast is sized for a bulb rated 9 watts not 15 watts.

 

[mgmine]

It won't work but you can always install a second light inline if needed.