Not sure about wattage, but I would recommend using NO bulbs with NO fixtures and same with HO lighting as well. Don't mix and match NO for HO. Same goes for T8 vs T5 bulbs, don't mix them. You can harm the ballasts, bulbs or both.
I'm pretty sure he's talking about power compact bulbs and not linear fluorescent bulbs (ie, the big U shaped bulbs with 4 pins at one end). They don't make linear fluorescents in 55w or 65w.
If that's indeed the case, then yes, the two are interchangeable.
That's true of CFLs, but it doesn't really hold for most fluorescents. If you use a lesser rated bulb, you'll end up overdriving it (VHO) unless you have a smarter ballast. The 55w/65w thing is just with those two bulb sizes.
I'm pretty sure he's talking about power compact bulbs and not linear fluorescent bulbs (ie, the big U shaped bulbs with 4 pins at one end). They don't make linear fluorescents in 55w or 65w.
If that's indeed the case, then yes, the two are interchangeable.
Depends on what you're wanting to grow. It will be best for a low to medium-low light aquarium, depending on the quality of your reflectors.
And just so we're clear, yes, you can use your 55w in a 65w PC fixture, although I do recommend you get a more FW appropriate bulb.
It's mostly just ugly. Plants can use blue light just fine.
And is it true that algae utilizes blue light very well? I read that somewhere but have heard nothing to back it up
I don't think it much matters. I think the only reason that may be is because plants tend to favor more of the red spectrum where algae has almost no bias in regards to its demands. I know aqua chem won't agree but ive seen a difference in plant growth from focusing on the red side of the spectrum as opposed to the blue. Can you grow plants in blue light? absolutely I've done it. But most will agree that you'll have greater succes with all plants between 6700-10k. But I think your PAR is above all the most important. Sorry that got a little off topic lol
Certain types of algae have been shown to prefer blue light, but most studies have been done with sw species. Plants will use both red and blue light readily. Interesting to note, though, is that the pretty much undisputed "best bulbs" on the market, Giesemann Aquaflora and Midday, are fairly unique in that they have disproportionately greater blue spectrum than other brands. I've used blue heavy and red heavy bulb combinations and have never really seen a meaningful difference in plant growth.