I'm have a 29 gallon aqurium with a 130 watt compact fluorescent light fixture. I've had the tank over a year now and now I'm trying to plant it. I want it to be a south american theme. I have regular gravel in it as substrate and was wondering if I should take all this gravel out and replace it with something like Eco-Complete or flourite or if I could get away with mixing a bag of this in without taking the regular gravel out?