AllPondSolutions 9w PLS UV Lamp / 2 Pin Lamp - Vijver/Aquarium

The 2-pin base clicked in perfectly, no fiddling or forcing needed. My pond water cleared up noticeably within a week, so it's doing its germicidal job even though I can't see the UV light working. Just remember to swap it out yearly since the output fades before the tube actually burns out.

After nearly a year, my pond UV clarifier was getting weak, and this replacement bulb got the green water cleared up within a week again. The 9w PLS 2-pin design was a direct swap, no fiddling with adapters.

Swapped this into my filter housing and the algae cleared up within a week, which tells me the old tube had been spent for a while. Being 2-pin it only fits one way, so alignment was fiddly for a second, but it clicked in fine and the water's been clear since.