I have used eco-complete and it works great for plants. Not as good as soil substrates but still better than sand.
Eco-complete and Flourite have high CEC so that's why it's recommended over just using sand. It will not breakdown and yes you do need to dose the water column, you need to do that with any substrate unless your substrate is made with organic material like dirt/potting mix. AS you can do without dosing for a while, however, this is all contingent on your use of co2. Without a sufficient amount of carbon, the plants uptake of nutrients will be much slower, and will not exhaust your substrate as quickly. Another factor is your plant selection.