by mewickham » Mon Jul 20, 2015 11:55 am
Well, I like to mix laterite (an iron-rich type of soil) into the lower half of the substrate, but you would have to empty the tank to do it. (Don't sterilize the gravel, just rinse it clean.) You could set it right back up and safely add the fish-- but the water might be a bit cloudy for a couple of days. Alternately, you can just plant the plants and then buy laterite tablets or some of the various plant tabs to poke them into the gravel around the plant roots.
And, of course, make sure you provide enough lighting. Generally, 2-15 watts of light per gallon is recommended.
Be sure you buy truly aquatic plants. So many of the stores, especially the chains, sell marsh plants that live a limited time underwater.