I've decided to change out the fake for real plants in my 20H. wanted to know what some good beginner plants might be. Also, can I just mix in some plant substrate to the gravel or should I try and replace most of it ?
Good beginner plants are java fern and java moss. These pretty much won't die unless you really mess up. Survives in low light.
What kind of gravel do you have right now? In most cases, it would be okay to mix unless it is gets too deep (substrate that is). Might want to take half of the gravel out and replace it was the same volume of plant substrate.
what kind of lighting do you have on your tank? for the most part I have had success with java moss, anubias, hornwort, java fern, java lace fern, watersprite, and anacharis in stock lighting set ups (lowlight less than 2 watts per gallon).
Just the stock light strip that came with the hood. I can upgrade that if I need to. I have Java Moss in my tanks already and it seems to be doing well.
Anubias will grow in a closet with the lights off. But they grow slow and are algae magnets for that reason. They get most of the nutrients from the water column so no substrate is needed, in fact I think they grow faster when tied to driftwood and their roots exposed to the water.