I have the same 300 gal tank and I run 24 t5 bulbs on it. I set up the tank about 30 months ago and it is doing very well. My fixtures are tek (the old ones) and I use giessmann bulbs (50/50) actinic+, aquablue+. The tank is 90% acro's and all accept maybe 2 are growing well with great color. I do change the bulbs every 6 months and I run the lights 12 hours a day. My water quality is kept up and checked weekly. And I do a 15% water change every 2 weeks. I did a lot of reading about lights before setting up this tank and in my opinion the added cost of ATI is a cost I could not justify to my self. A big draw back is that the reflectors need to be changed every 18 months, my fixtures are laying on the tank frame and the bulbs need to be wiped down every month. Hope this helps.