Which T5 should I get

[Canadian]

Originally Posted by Myka

You're comparing grapes to raisins. 8 bulbs x how many watts? 54w? That is 432 w (quick math I hope that's right haha). You can't compare 432w of T5 to 250w of halide! That's not a fair comparison. PLUS, you have to use the same Kelvin bulbs in order for it to be accurate. According to Steve (Stir Crazy) actinic bulbs put out a false high PAR reading as well, so if you have actinics in your 8 bulb fixture you're not getting an accurate reading.

In order to compare T5 to MH you need to make sure all the variables are equal...this is where a lot of people fail, and come up with misleading numbers which they now think is the be all end all.

If you're going to calculate the T5 as if it's going on a 4 foot tank (54W) then you also need to be reasonable about the application of the MH - no one is going to try to realistically light a 4 foot tank with a single 250W MH. So consider that the above example is likely 2 x 250W MH in a real-world application (although that's purely speculation on my part as I wasn't the one making the claim - but it's certainly a reasonable consideration).

Secondly, very few people actually recommend running T5HO actinic lamps. A typical application would include lamps measured some where around 450nm but generally not pure "actinic" 420nm. And as an example even a 250W AB 10,000K on an M80 ballast has its largest peak at 420nm (actinic) so I suppose it's producing false high PAR readings?