Yes, I have been reading the "light intensity" thread under the Articles forum, but it isn't helping me make a decision. There seems to be a ton of variables in this lighting stuff.

I've been researching lighting for a 120G (48"x24"x24") non-CO2 tank. I'm fond of T5s, but they are rather strong for a non-CO2 tank, at least for the amount of area they cover. If 2 x 48" (54w) T5s covered more area (front and back), I would give that a try. I do not know much about T12s, T8s, T6s and the like -- but I am not immediately drawn to them from my research.

Anyway, I am now leaning toward 4 x 54w T5s and simply raising them up as high as necessary to reduce the light appropriately. I do the lights-hanging-from-conduit setup, so it would be very easy for me to adjust light height. I could also turn on 1 & 3 for half the day and 2 & 4 for the other half -- there are many options I could try with this. Other than wasting electricity and the extra cost, I feel that this would be a decent solution. Do you agree? If anybody has other possible ideas, I would enjoy hearing them.

Why install so much light you have to raise them high and waste the light by lighting up the floor? For a non CO2 tank I doubt that more than 2 of those T5 lights are desirable. If you space them properly they will cover the whole tank.

That is good news for me, Hoppy. If 2 of the T5s will do the trick, all the better ... easier to build the fixture, cheaper, less waste. This was actually my first plan, not sure how I started thinking that only 2 of the T5s wouldn't give me enough coverage. Anyway, that's why I asked. Thank you.

2-4 would be okay, 4 is on the high side, 2 on the low side.
2 would run a 75 gal nicely, 4 and CO2 would be nice also.
Depends on plant choice also.

also, you will need to space the lights way apart to get decent coverage in the tank, say 16-18" apart with two, whereas 4-5" spacing works well with 4.
Also, run the 2x54 for 10 hours and the 4x54 for 2 hours etc.

You have some options.
On decent sized non CO2 tanks, and low light CO2 tanks, T5's are ideal.

Regards,
Tom Barr