Ok...i'll try to answer what I can.
If you want to keep live plants properly...ie a planted aquarium, you need to look into all aspects of your aquarium.
Plants need a good, nutrient rich substrate and quite often, a sandy one too. Lighting should be bright....a total of at least 2.5 - 3 watts of lighting to every gallon of water. The more light you have, the more CO2 needs to be added and because of the lighting and CO2, you will have very good plant growth which will mean you will need to add liquid nutrients to feed the plants.
However, no one that wants to keep plants successfully adds oxygen. This is because it interferes with the amount of dissolved CO2 in the water (ie it disperses CO2 quickly at the water surface). Instead, what a lot of people do is to inject CO2 during the day and use a solenoid valve to shut it off at night when the plants don't need it. When the CO2 is shut off, an air pump can then be added on a timer to add O2 at night.
A very good site for planted tanks is
http://ukaps.org/forum/
Go and have a read
As for a UV....personally i think they're a total waste of time. I never used one on my reef aquarium and only use one on my koi pond to keep the water clear.
As for your filter media, i'd probably have the sponges at the bottom (presuming the water enters the filter at the bottom)...in other words, the sponges should be the first thing that the dirty aquarium water touches so they remove the solids before the water reaches the biological media.
Again
http://www.uk-aquarist.com/index.php?&act=idx is a good forum for general fishkeeping.
Hope this helps a bit