I've created planted tanks in many substrates over the years, but the hardest to keep plants rooted in has always been sand for me.
I've used sand and gravel of many grades and shapes, I've used just aquarium soil without a cap. I've even used coir as a substrate when raising killifish and a few other species.
It all depends on the type of fish that will be in the tank, sometimes you really do have to suffer as a fish keeper.
I find that with sand I have the best results when I have an inch or two of aquarium soil capped with an inch or so of sand. The soil really only adds a temporary boost of nutrients, so you do have to add root tabs still, but the larger particle size and roughness seems to allow the roots to hold better.
I also find that with filter feeders or species that like to dig it is best to give the plants a couple of months to really establish the root structure to give them the best chance of holding on.
That's less important for gravel or coir, but those substrates are less suitable for bottom feeders anyway.
I've used sand and gravel of many grades and shapes, I've used just aquarium soil without a cap. I've even used coir as a substrate when raising killifish and a few other species.
It all depends on the type of fish that will be in the tank, sometimes you really do have to suffer as a fish keeper.
I find that with sand I have the best results when I have an inch or two of aquarium soil capped with an inch or so of sand. The soil really only adds a temporary boost of nutrients, so you do have to add root tabs still, but the larger particle size and roughness seems to allow the roots to hold better.
I also find that with filter feeders or species that like to dig it is best to give the plants a couple of months to really establish the root structure to give them the best chance of holding on.
That's less important for gravel or coir, but those substrates are less suitable for bottom feeders anyway.