do i really need a new light fixture.

light is light is light... t5s are favored because of the small size and high output you get more light for q given area, u can easily build a fixture with reflectors for each bulb which maximizes the amount of light directed downwqrds to aquarium and not lost as heat... also they are skinny so you can fit a lotof them over a small area. so high output (read more watts relative to bulb size) + individually contoured reflectors (not all fixtures have these) + ability to fit many of them over your tank = more light.

but watt for watt all fluoros ho or not put out relatively the same amount of light, and mhs basically put out the same watt for watt but have better penetration and have an output advantage at 250w and up.

in other words 40w of t8 is superior to 36w t5. wattage is what matters not he size of the bulb. now if the t5 fixture has a better reflectr(s) it wins. one thing to consider is if u are running a frag tank, using a warmer full spectrum bulb like a 6500k bulb will give you a lot better growth, but wont be visually appealing. if ur using 10k and acinics on your frag tank with those watts u are wasting your time but with a 6500k u should see reasonable growth. iwasakis are the best par rated bulbs available and thy are like 6700k (mh tho) they are ugly lights but grow corals very well.

so yeah i would run those t8s go to hardware store and get some ~6500k (daylight) spec bulbs should work out nicely

dont run out and buy an overpriced t5ho fixture w/expensive
10k and actinic bulbs. a t5ho at 3.6 wpg is still not going to grow clams, actually if u run NO t8s with 6500k bulbs to the zooxanthellae in the coral
it is a LOT brighter because it produces more red, green, and yellow light which activate photosynthesis more than blue light.

usually wih aquarium lightting what looks best is actually the least
favorable for growth.

 

Basically agree with everything you said. The only thing I would say additionally is that using 6500K bulbs will be good for growth, but you won't get a good coloration from the corals. If that's not a real issue, then go for it, But since it's a frag tank, I would use 10-12K bulbs.

 

right but theyll color up when placed under display lighting after a few weeks/days

 

so would the lighting fixture i have work but just get some different bulbs?