Potting soil substrate

My 36 has been running for around 4 months and the plants wilting away in a straight gravel bed. So, since I had good biological established in my trickle filter and sponges, I decided to jump the tank to potting soil. Took me 1.5 hours start to finish. Fish are doing well and other than a little cloudiness, it worked. Don't know if anyone else has tried this, but I emptied the main tank and left the sump full. Pulled all the gravel, and then put in the potting soil with gravel on top. Then as I simultaneously filled and siphoned until the brown silt disappeared. Then I put back 50% of the original aquarium water and fish. No one seems unhappy. I had to do another 50% water change the next day to get out some cloudiness, and now all is fine.
If my plants take off, I hope to slowly remove bioballs from my sump until I am running exclusively on plant filtration and a couple of sponges for mechanical. I will not be doing gravel vacs anymore and hopefully this will enable me to forgo co2. We shall see.

My plan is to remove 15% of my bioballs and then test for a week, and then repeat. I plan to put water lillies in the sump which gets plenty of window light in place of the bioballs.

Any thoughts

If all works as hoped, maintenance will be minimal. The co2 will come from decomposed organics. I will hopefully reduce co2 gasoff by removing the trickle filter and reducing surface agitation. Of course introduction of co2 injection would increase plant growth, but I want to attempt to create a balanced system. I realize this will probably mean a reduction in fish population, but we will see.