I don't think EcoComplete is available in a fine grade such as sand. Years ago they offered it but is was discontinued.
Earlier this year I carpeted my tank with DBT. It went well for about 5-6 months and then the carpet started to lift up. I was using EcoComplete, PPS-Pro ferts, moderate to heavy CO2, and a pair of Finnex fixtures in a 20g long. For the first 4 weeks I kept the fish in a different tank and this allowed me to be generous with the co2. It was nice while I had it but I just could not keep up with the weekly trimming; once it gets "full" it tends to grow over itself. If left unchecked, I found that the undergrowth would not do so well (yellow, decay).
Would have I attempted this without CO2? Probably not. Is glutaraldehye (or Seachem Excel, API CO2 Booster) sufficient for growing DBT? Maybe. Would I have used a different substrate? Definitely. Something such an ADA aquasoil or similar product due to its nutrient content and grain size. EcoComplete, like sand, is not full of nutrients on its own. Unlike sand, it has the ability to weakly bind certain molecules, some of which are vital for plant growth.
I've had better luck growing DBT in a terrarium. I even have some growing outside under a waterfall.