Very nice! What lighting is that? Think I see a led satellite and some t5's?
With high/med lighting you will need to start dosing fertz (n-p-k & micro) easiest and cheapest way is to buy dry fertz and mix them with water in bottles and dose them wet.
Link for great fertz:
http://greenleafaquariums.com/aquarium-fertilizers-supplements/pps-pro-fertilizer-package.html
Dosing:
http://www.aquaticplantcentral.com/forumapc/fertilizing/15225-estimative-index-dosing-guide.html
Not sure what you use as a co2 reactor but if you run a canister or sump/wet dry check out rex grigg DIY reactors, they are about 12-15$ to build and have 90%+ co2 dissolution into the water making your co2 more efficient. Ceramic Diffusers aren't exactly the best option for such a big tank!
I recommend getting fertz ASAP because with high/med light and injected co2 your plants are hungry! (Its like having a dog that constantly runs and plays burning lots of calories so replenishing those are important for good growth!) More light more co2 makes plants grow faster thus absorb nutrients (fertz) much faster!
×Go S. Vettel #1 Infiniti Redbull! 4x WDC!!! Congrats on another flawless title×
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Cheap way to decrease nitrates and keep your fish healthy: http://monsterfishkeepers.com/forums/showthread.php?t=504763