34 inch bulbs in 48 inch system?

I just drove to my LFS which is about 40 min. one way and got the bulbs I need. I asked the "fish technician" at the store if my system needed 34 or 48 inch lights (forgot to measure before going) and he said oh yeah get the 34... my question is will there be that much difference using the 34s instead of the 48s that should be in there? They are the same wattage/price.

 

Er, unless I'm missing something, your new 34 inch bulbs won't even fit in the fixture you have, if it needs 48 inch bulbs.

 

Bulb lengths need to match the length of the fixture. The output type of the bulbs need to match the ballast's output also. Measure your fixture to be certain but I bet you have a 48" fixture so you will need 48" bulbs.

 

I'm confused as well. Bulb lengths are not interchangeable.

 

You know, thinking about this again, possibly this is because you bought PC bulbs that were 34" instead of 48"? The assumption I made was T5. I don't know if PC all have the same pin layout, but shorter bulbs might work if the connectors are the same. I would personally return them and get the right size, though.

 

Good point.

 

Yeah I'm going to return them and for those that are confused... the bulbs are all standard 420/460nm actinic/blue actinic 98 watt PC no matter what the length. They are square pin and only "snap-in" on one side of the light system. I put the 34'' bulbs in and they work fine... they just don't reach the entire length of the system as it is made for the 48'' bulbs.

 

Good idea on returning the bulbs/fixture. PC are nice but their reflector design is very limited and limiting and really hurts their performance. T5HO are far more efficient also.

 

So you would recommend getting the dual daylight bulbs? 6500K and 10000K? I like the blue actinic look though.

 

Get 10000K/460nm blue blulbs that will give you the best PAR and color mix. You could do 6500K/10000K for one if you want.