After one month of DSM, I filled my tank, photo period length suggestions wanted

[beedee]

I filled my 12g Long Iwagumi (tank is in my signature) this past Wednesday evening. I did a dry start for a little over a month, specs listed below.

Dry Start Specs:
Lighting: AquaticLife 36" T5HO, 1 6500k bulb, 1 Roseate bulb
Light Height: Using stock issue legs that came with light, elevated about 3" above substrate.
Light Diffusion: 3 layers of window screen between the splash-guard and the bulbs
PhotoPeriod: 12 hours
Flora: HC, DHG
Substrate: ADA Amazonia, "New"
Hardscape: Seiryu-like Stones

So as I mentioned, I filled the tank on Wednesday evening and have been doing 50% water changes everyday so far, and the tank appears to be doing well. I haven't noticed any melting of the plants, or any other ill effects. I reduced my photo period to 6 hours, and am running my co2 24 hours a day (don't have a solenoid yet). I'm using a brand new eheim 2213 for filtration, and the flow is really good, I even have it turn down a little bit.

My question to you guys is, what should my target photo period be at now that it is filled? Also, when should I start introducing my NPK +M? I haven't dosed anything at all yet.