I want to build a light for my aquarium out of LED's, and need to know...?

Question

Which resitor to use that will allow the most power to go through to my LED's that will give the most light. Each LED maxes out at 3.6 vts.

Answer 1

you will need to know the total wattage of the leds.  you will need to build a rectifier to change the ac wall current to dc.  you will also need to step the voltage down from 120v to say 12v.  once the wattage is known you can calculate the resistance needed using watt's law.   power in watts divided by current in amps squared equals resistance.  all of this information is easily found on the net and youtube.

Answer 2

you can already buy such a light

Answer 3

first you will need a transformer / power supply to bring the voltage down to something usable for leds,  then you'll need to decide how many leds you want.  then you'll have to go out and buy those leds.  they should come with specs that will tell you what voltage they prefer and how many watts they consume.  there is a lot of variety out there, so we can't really answer your question simply.  once you have an LED circuit design, and know the specs of the LEDs then the rest can be calculated.