Looking forward to your progress as I have a 75 gallon myself that I am planning to start in the near future. How will you place the light - suspended? on legs? right on top of the tank?
According to Hoppy's lighting tables (http://www.plantedtank.net/forums/li...t5-t12-pc.html
), 4x54w T5HO can be too much lighting for a 75 with respect to how it is placed. I thought about getting a 4-bulb fixture too, but am not sure yet.
The retrofit will be attached to the top of the canopy, which will be about 13" from the water surface i believe. So, according to Hoppy's chart, 3 bulbs will give me medium light, and 4 bulbs will give me high light. I'm hoping to make this a high-light tank if i can keep up with the water change/fert schedule.
I was looking forward to see your new 75 gallon set up and it was sad to see your 150 go. Are you going to switch the 5 lb to a bigger tank in the future? It's not going to be fun running back and forth from the co2 refill place every month or 2.
After everything is up and running and when i have some spare cash, i'm definitely going to upgrade to at least a 10lb.