Eco-complete alone is fine but it puts more emphasis on the use of root tabs. Eco-Complete will collect minerals and nutrients from water column dosing as well but tabs will be necessary for stemmed plants.
I personally used Miracle Grow Potting Soil (about 1-1.5" deep) and capped that with another 1-1.5" of eco-complete. Root tabs, I found, were less necessary.
Yea - I had read about a number of folks doing that; I assume the Miracle grow is cheaper anyway. I could take back one or two bags of eco complete and get a big bag of miracle grow.
Also, if 75 PAR is accurate, then you will indeed be pushing the medium-to-high light boundary. If you're not heavily planted, I think algae problems are almost guaranteed.
I actually don't know if that is accurate or not. I tried to figure it out based on the PAR sticky on this site which does a 4-bulb T5HO from them ... so, just used math to figure it out for myself. Aquatic Life doesn't publish PAR values in there spec sheets that I can see.
After looking further on the site, I see a lot of good things about Finnex. And, according to this thread
, the 36" should give a little under 60 PAR at the center of the tank going down to below 50 at the endges. That might be a little more manageable. More expensive on the outset but would save money in the long run.