The difference between t5 and t8 is... T5 lights are smaller in diameter and use less power. Thus allowing for smaller fixtures with more bulbs. As far as lighting goes with a 3 feet deep tank you are going to see some strong lights to penetrate that far. personally I would skipp the t5 lighting and led
lights and go with a metal halid lighting system if you are wanting to place corals at the bottom and have any other corals. as far as the specs on light. I would go with a combination on actinic lighting and some type of high k
value lights such as 10000k or 14000k. Actinic lighting peaks in the blue spectrum allowing for it to penetrate deeper in the water. 5000-around 10000k peeks in the red spectrum. The higher the k
the more blue the light looks. algae and photosynthesis do best under a 6500k light. But for a reef tank that lighting would grow corals fast but give them a ugly color. That is why reef keepers use 10000k to14000k lighting to bring out the color in corals. Any other questions you have?
For t5 lighting I would go with a 12 bulb fixture.
For metal halide I would go with 2 250watt bulbs supplemented with 2 t5 actinic lights.
lights I don't know to much on but I would suggest looking for one that has high watt led
such as 3 watt led
for the main lights.
The cheapest in the long run would be led
lights but will take a few years to pay for it's self. Mh
are prob your best bet at the moment.