Adding soil to established tank
I have a 5.5 gallon low-tech tank with just a betta, an anubias, moss and java fern. I've always just had white gravel in there but lately I haven't liked the way it looks (not that clean), and have been preferring a more natural soil aesthetic. I also want substrate that'll be better for the plants, as I'd like to add a few more and try my hand at carpet plants (tricky enough as is without CO2).
I'm new to planted tanks but after some research I'm leaning towards Tropica aquarium soil. It's less ammonia rich than ADA and I can easily get it on Amazon. My concern is how to make the switch from the gravel to the soil without hurting my betta. I don't mind the work of taking apart the tank as I'm moving soon and will have to drain it anyways, and it's a good opportunity to redecorate/add the new plants, but I'm worried about water parameter changes.