Well, the light fixture will need to be upgraded, either through a retro fit, or a new fixture entirely. I suggest power compact lighting to get more lighting with less space used. You'll want at least 2x55 or 2x65 watt's over that size of tank, and even that's only gonna be at the lower end of lighting levels. $100-$200 for compact lighting.
Technically you could overdrive your current fixture, but it requires some experience, and a certain comfort level, with working with electrical wiring. And OD'ing bulbs makes them burn out faster...typically needing to be replaced after 4-6 months, rather than 9-12 months.
Once you hit 2 watts per gallon, especially with power compacts, you're going to need CO2
injection. A 5lb CO2
tank and a regulator will run you around $150-$180. Then you need to build or buy a reactor, so a max of $50 for that.
If you do inject CO2
, you'll need to know your Kh
levels. As long as you have 3degrees of Kh
, you can inject CO2
safely. You'll also wanna lose the HOB
filter, as it'l likely outgas some of your CO2
The lighting levels you choose, along with CO2
injection, will determine the rate you'll need to dose ferts, as well as your plant selection.
On a tank your size, I will always recommend buying bulk, powdered ferts, from a place like www.gregwatson.com
SeaChem and Kent are fine ferts, but much more expensive than their powdered counterparts.