Marine land 56 gallon column tank. I think that the depth and height this tank offers would be ideal for a planted tank. I envision staggering the aqua-scape to create interest at every height of the tank. I want it to be lush and full of life.
30" W x 18" D x 24" H 30" wide is a little bit awkward for lighting, but something can be worked out. 18" deep is pretty good to make a nice 3-D effect. Good for aquascaping. 24" tall is good for the taller plants, and things like driftwood. A bit tall for rocks, though. They would have to be quite massive to work in that tank.
What substrate do I use? I like Safe-T-Sorb, but there are others. With the black stand and trim maybe you want Eco Complete or other black substrate?
Do I just add all the plants at once or should I do it slowly like you would add fish to build up the bioload? Read the fishless cycle. (Next post)
Ideal filtration and devices for water circulation... I would use a canister for this size tank, plus a power head. My personal choice would be a Rena XP3 and one of the larger Koralias. I use the older style #4 for tanks of about this size. Most of my tanks are 4' long, and vary from 12" to 18" in either height or depth. The one I have that is the closest to that is a 46 gallon bowfront. I use the XP3 and Koralia 4 on that, too.
Current lighting I have is a 10k 65w daylight and 65w blue actinic is this enough? I would not use those for plants. The K values are not really a reliable way to gauge if the lights offer the right spectrum for the plants, but more often than not those are the wrong ones. Especially the Actinic. That replicates the tropical sun in a coral reef. Fresh water plants come from more shaded locations, and use different wavelengths than the algae component of corals. I use a plant specific bulb, high in the wavelengths that plants use the most of, plus a 'daylight' bulb that gives the wavelengths that make things look right to my eyes. Read up about PAR. Get the absolutely best reflector you can with that tall a tank.
Do I need a c02 tank or can I simply supplement with liquid c02...? Some plants are just fine with glut (Liquid carbon), but for the best, go with pressurized. That size tank will go through a lot of glut ($)
Dry fertilizers will be the way to go, also. Never mind all the fancy bottles you see in the stores. They are just bottles of water with a pinch of fertilizer. Do not pay for water, just buy the ferts.