Do I need plant specific substrate if I use liquid fertilizer?

I know a good amount about OUTDOOR gardening, but am learning about aqua-gardening.

Since most of the readily available planted tank substrates either look too silly, come in too large a quantity, or cost a LOT, I'm curious if it MUST be used IF I am already adding a little liquid fertilizer to the tank water?

I know that some types of plants must have roots planted, but is larger size gravel too large for those roots? Do they need a substrate touching their roots just like garden plants do?

In my case, I use a Liquid fertilizer once every 2 weeks but for my floating plants and water column-feeding plants (epiphytes). My tank has a 2-layer nutrient system (JBL Aquabasis Plus+ Aqua soil) capped with gravel. I don't have any issues with plant growth at the moment. For my root feeders however, I will be adding root tabs in the coming months as my tank reaches 6+ months old. I don't know if this is needed but it's nice to have the peace of mind there are still nutrients for the plants. As for a tank with non-plant-specific substrate. I don't know a whole lot about aquarium plants in general but I've heard if you have a "seasoned" aquarium plants usually do better because the fish waste is converted into nutrients for plants deep in the substrate. My old aquarium lasted for 2+ years with no root tabs, no liquid fertilizer, and no gravel Vac as the fish waste was the plant's food. I only had a mesh bag at the bottom filled with aqua soil and a good 3-4-inch cap of sand and pea pebbles. I will admit that the aquarium took a long while to grow in but the results spoke for themselves after 6/8 months. Re-thinking about it now maybe that's because they reached that aqua soil

(OLD AQUARIUM)


As for the size of the substrate, this tank had a large amount of pea pebbles going from the middle to the back to create height (where that rotala was planted) And Its roots went through them pretty well

One other thing to consider is a Walstad method aquarium. I've been considering this as another new aquarium mainly for its lower cost. But again my knowledge of that is far too little at the moment.
More experienced members will probably give you a better answer

I think the short answer is no. Soil substrates can leach into the water and also eventually lose all their nutrients, although I know plenty use them with no issues. I just use a sand substrate, put root tabs in every few months and dose with liquid fertiliser every water change.