Ive got a rio 180 with the standard 2x t8s which are either 30w or 36w. Ive also got an interpet t5 starter which is 54w. My plant growth is ok, and i have pressurised co2. Will see much of a diffwerence with 39w t5s?
T5 will definately improve your lighting output, the only down side is that you will have to increase your fertz and Co2 (if you have Co2) as you will require the balance between the three elements: Light / fertz / co2 see attached doc for the "the Golden Triangle" http://www.thegreenmachineaquatics.com/ ... fe%20Nitro
The difference between T8's and T5's basically is the lumen output per circuit watt, with the T5 being more efficient. Since you are proposing to get rid of a lower power T8 to a higher power T5 then you will certainly have more light to play with .
Cro - The only reason that I can see for a tank to look better with a T5 (apart from the aesthetics of the luminaire itself) is the type of lamp that you have used, for example you may have had a T8 lamp with a colour temperature of 4,000K and now have a T5 lamp with a colour temperature of 6,000K? The other reason could be to do with the colour rendering of the lamp, you may have had a halophosphor T8 but now have a triphosphor T5? You can buy T8's or T5's at many different colour temperatures and you can get either as a halophosphor or triphosphor.