I dose C02. Right now it is just a Fluval ceramic diffuser straight into the intake of the canister filter. The idea was to use the canister as an inline diffuser. It works at lower bubbles per second but at the higher end that I'm going for it tends to build up gass in the canister. I have to shake the canister 2-3x a day to "burp" the gas out. This is not ideal so I purchased a used DIY inline diffuser from someone on APC. I also purchased a magnetic solenoid valve so the gas turns off at night when the plants no longer use CO2. Currently the CO2 is on 24 hours and I run an air pump to gas off the CO2 at night and increase the O2. At night the plants use oxygen and compete with the fish to breath. Once I get the solenoid valve I'll hook it all up and post some pics.
I use dry ferts bought from AquariumFertilizers.com. My fish bioload is high enough that I don't have to add Nitrogen (Potassium Nitrate) or Phosphorus (Potassium Phosphate). I dose liquid C02 (Excel) daily, Micro nutrients (CSM +B) every other day and also Potassium Sulfate 3x a week. I do a weekly 50% water change and add one teaspoon of Baking soda + one tablespoon of GH salts (kents R/O right or Barr's GH booster). I live in Sacramento CA and the water is very soft. I will add Iron if I see my pogostemus erectus get too yellow, maybe once every two weeks.
Lighting is now on 9 hours a day with a 4 hour "burst" cycle (additional 108 watts of T5 lighting). Initially I had them on 12 hours and had some algae issues. Now that things are grown in I plan on lower the lights to only 8 hours a day. Instead of one 4 hour burst, I want to do 4 seperate one hour bursts. I'm hoping by doing this I can further increase my C02. The idea being that the C02 will increase during the lower light times then the burst will suck up the excess before it gets too high. I'm sure it will take some tweaking.