For Most aquariums :  Maximizing the amount of light plants recieve has a beificial effect, but the are many ways in which light get lost in the aquarium as well.

Light from a fluorescent tube for example is emitted in all different directions ( using a shield to direct light down towads the plants an water helps alot.

Some light is refracted from the waters surface.

Some light is lost through the aquarium glass.

Condensation trays if left unclean will stop alot of light.

Particles such in the water such as algea will soak up a large amount of light. 

Light will also pass teh the water and its spectrum is changed as it is absorbed and coverted into heat energy.

So if you want to carpet certain plants they will on receive a small amount of light emitted from the bulbs. 

Large plants can also block light in upper levels  of the aquarium and minimize light reaching lower smaller plants.

Florescent lighting: - Is a cheap and good way to go for beginners or people who do not want to spend a fortune on lighting but still want a descent planted tank. ( You will just need a sufficiant amount of it) But that is ok because they are one of the lowest energy users.

- florescent light doesn't penetrate to the bottom of the tank unless you have a good amount of it as well.

- You will also have to change the bulbs forom every 6 to 12 months. As they loose their intensity but will still appear to work fine. ( the plants will know)

- pink phillips t-12 bulbs work amazingly and are alot cheaper than aquarium t-5s or t-8s but give off a pink hue that the plants love. If you add in a white buld or light blue it mellows out the pink.

Florescent lighting is Great for shallow tanks or smaller tanks  In a tank that is 15in (38cm) deep or less i would use 1.5 - 2 watts per gallon of aquarium water but for deeper tanks you can go a couple different ways.

DIY LED / LED SYSTEMS:    LED lighting is another low energy cost of lighting that produces high lighting environments for plants. ( But  unless its DIY it cost a shit load of money right now and the ones you buy are usually not good enough and you end up adding more.) Plus I read  that the  technology of LED aquarium lights does not succeed the technology of an LED flashlight! That is why i make my own. ( not literally)

With LED you almost never have to change a buld.

They look amazing.

High light for high light plants.

You have to watch for algea sometimes switching to high light right away triggers and algae bloom.

SO like I said you can either buy 2 or 3 or the 400$ each systems or build your own for less than 200 that puts out far stronger light thank aquarium LEDS.

Im going to post some links to the best DIY LED systems that i use in more that 4 of my tanks and plant farm tanks and tables.

The first video has 2 parts to it. They are pretty much a normal kitchen or bathroom fancy fixture that runs 50 watt metal halide but you can convert to gu10 LED bulds that run i believe 15 watts and put out the same amount as a 50 watt metal halide.

You can get all of this stuff at home depot, home hardware, rona ect.

Here is the first DIY led light system that i used 2 of...

 http://www.youtube.com/watch?v=MzVEmJy7yHY   ( click the link in the video to watch part 2)

The next video is a system i use on my planted dirt tank and my plant farm tanks. Its basically outdoor LED flood lights that put out 6500k of light. You can get different sizes im using one that  runs at 20 watts or somthing light that and puts out the amount of light a 100 watt bulb does.

I used them in reptile heat lamp light shade that cost probably 10 bucks.

The bulbs are a but prices mine are phillips and they are about 35 dollars each but they last for 27 years and if you run it at 3 hours a day its says on label it will cost you 125 bucks in those 27 years.

http://www.youtube.com/watch?v=To1FkOA0lgM  ( After this first video wayne has used i think about 6 or 7 of these lights ever since in his 125 gallon.)

This last video is one of my fav lighting systems that I only have on one tank right now but i love them!

Same as the spot light  but a different kind and style. CHECK IT OUT! 

http://www.youtube.com/watch?v=nGhWziY_zh0

Like I said I think these are the best and cheapest ways to light your aquarium and i hope this helps you figure out if you wanna spend alot of money and have a nice tank or barely anything and have and amazing tank.

CHEERS!