Fertiliser Substrate under gravel substrate
Is it possible to add plant substrate (not top gravel) to a tank after it's already set up? I added some to my small 40l tank which already had water, and the water was full of brown sediment for 2 weeks. Luckily it's just in the setting up phase, but I didn't want to remove the water to stall the cycle.
In any event, I plan on adding more plants to my 230l tank and might raise the gravel level on one side and add plants there, and if I do, I'd like to add some substrate to help fertilise the added plants.
Is there any way to do this? I am only in the preliminary thinking phase so haven't googled yet for ideas, I just want a quick answer here first before I start any major research.
Thanks in advance,