Advice needed, PL or FL?

[stocker]

This is for a DIY light for a 2ft low-maint/tech non-CO2 tank. I already have a reflector that is originally meant for FL, but a PL can fit in there with the proper clips without problems, and intend to use a e-ballast. Should I do a 2x18W FL or a 1x36W PL? PL does not really cover the tank end to end but I don't think there is much concern as most are low-light plants, on the other hand, FL is cheaper.

Any comments/advice? thanks!

[Mason]

Maybe you can even save all the cost. You might want to put them under the sun?

[|squee|]

FL then. You can have the additional choice of switching on only one 18W tube if you feel lights are too strong.

[stocker]

FL then. You can have the additional choice of switching on only one 18W tube if you feel lights are too strong.

I tried connecting only 1 FL to my 2x20W e-ballast and the tube flickers intermitently, so I think it was designed to operate with 2 tubes only. I think 2x18W is quite OK, as I have a tank running that. That tank used to be running 1x18W and many plants cannot grow well.

[tawauboy]

the 2x20w e-ballast can run with only one tube connected.
try swapping the tube to the other connection and see of it works. or try replacing the tube.

[stocker]

the 2x20w e-ballast can run with only one tube connected.
try swapping the tube to the other connection and see of it works. or try replacing the tube.

Thanks for your advice, I've tried all that already. The unit is a Elbiru one. My tubes are Philips New Generation 18W and are farily new. With 2 tubes connected, everything is nice.